All language subtitles for [English (auto-generated)] Learn Solidity, Blockchain Development, & Smart Contracts Powered By AI

welcome to the ultimate solidity smart

contract web 3 blockchain developer

course Foundry Edition previously we've

done two other massive courses and

tutorials like this one of them with

JavaScript and one of them with python

and then now one in pure solidity and

combined those two videos have over 5

million views making them the most

watched blockchain developer educational

material on the planet and we're looking

to do it all over again we've learned a

ton for making those first two courses

and we've taken all of those learnings

from those two courses wrapped them up

into this one to make this one the best

one yet if you're more interested in

full stack development and working with

JavaScript the hard hat one is still a

phenomenal resource for you to get

started however this one has a ton of

advancements in it making it the most

Cutting Edge web3 developer course

period having done one of these videos

every year for the past 3 years I've

been reached out to by countless

Developers ERS who are now full-time

developers in the web 3 space making a

living doing well and contributing to

web 3 and there are thousands that I

have not met who have left comments or

left me notes and I know we're going to

do it again with this video If you're

looking to become a web 3 solidity smart

contract or blockchain developer or any

of those terms this is the course for

you and this course is for anybody and

everybody no matter your blockchain or

developer experience level and

additionally we're going to be using

artificial intelligence to accelerate

our learning progress and I'm going to

teach you not only how to become a

blockchain developer but how to work

with AI tools to make you a 10x

developer if you have a little bit of

developer experience before this this

course will be even easier to get

through but again don't worry if you've

never coded before and for those of you

who are already familiar with blockchain

and smart contract development feel free

to jump around the different modules and

different sections and grab the

learnings that you want I promise

there's a lot of cutting edge

information in here and maybe you need

to brush up so no matter if you're brand

new to coding brand new to blockchain or

you're an experienced smart contract

engineer you're in the right place

welcome to the edge of the rabbit hole

let's get froggy for those of you who

don't know me my name is Patrick Collins

I'm a smart contract engineer security

researcher and just lover of all things

web3 I'm one of the co-founders of the

smart contract auditing firm cyphon

average smart contract YouTuber

co-creator of web3 education. deev and I

live and breathe smart contract

development I absolutely love web 3

blockchain and smart contracts and I

love the power and the tools that they

enable us to use but not only that I

love taking blockchain developers like

yourself watching this video right now

on the journey to becoming a successful

smart contract developer I think the key

to web 3 to blockchain to

cryptocurrencies being successful is

having a phenomenal Foundation of

developers so I'm incredibly excited

that you're here with me and for those

you who don't want to become blockchain

developers the first two lessons of this

course lesson zero and lesson one are

foundational pieces of conceptual

information for you just to understand

how to get into this web three thing so

if you don't want to become a developer

just stop once we get to the coding for

my pythonistas here I'm working on an

addition of this course purely in Python

and Viper stay tuned for that as well in

any case I'm incredibly excited for your

journey this is a data dump passion

project of all the knowledge that I've

collected over the past few years of

working in this industry and being a

smart contract developer myself and at

this point I have the track record to

show that I am 100% confident that if

you follow along if you code along with

us if you follow me on this journey you

will come out the other side armed with

the knowledge to be a positive force of

the cryptocurrency and blockchain

Industry smart contract and solidity

developers are massively in demand with

an average salary being around

$145,000 a year and with AI coming in

place it's becoming even easier to get

up to speed quickly but only those that

understand the technology truly will be

able to take advantage of all these

advancements AIS get stuff wrong a lot

so we especially need the knowledge to

fact check whenever AIS get things wrong

being here you have the opportunity to

be a Pioneer ushering in the age of web

3 of cryptocurrency Blazing the trail of

where this phenomenal industry has yet

to go like I said this isn't the first

time we've done this we've already

helped so many developers get into space

and we're going to give you the Cutting

Edge most modern tools for Industries

like defi nfts Dow tokens upgradeable

smart contracts blockchains and

everything else that you can think of

once you finish this course it will be

abundantly clear what you want your next

steps to be and you'll have a ton of

Economic Opportunity at your fingertips

and opportunities to make a huge

difference in this amazing industry

however I can't just give it to you you

have to come with me on this journey you

have to take the step despite what you

might think you know cryptocurrencies

and smart contracts enable a more

accountable World a more transparent

World a more collaborative world a world

where promises can't be broken and

that's a world that I want to live in

we'll learn more about the purpose of

smart contracts and the purpose of

blockchain technology in lesson one of

this course and then of course we'll

teach you how to build it so before we

even get started I want to give you a

huge thank you for even being here on

this video and listening and being

interested in engaging in this

phenomenal technology so thank you for

being here and welcome to the rabbit

hole cuz we're about to drop down with

that being said let's get

froggy so let's begin our journey by

talking about some best practices that

way you can get the absolute most out of

this course and be as effective as

possible now there are two links in the

description that I want you to pause the

video right now go into the description

and click on and open up the first one

is web3 education. deev and the second

one is a GitHub link to a repo also

known as a repository with all the code

and all the lessons and everything we're

going to be covering in this video the

web3 education. deev site is an

education site that we're working on to

have all of this video and everything

else in all the Cutting Edge learnings

of blockchain developers in this course

in this site so if you enjoy written

context as well be sure to subscribe to

sign up for that so that you can be one

of the first people to know when it

launches and the second site is this

GitHub link this is going to be your

Bible for the duration of watching this

video it has everything that we're going

to go over it has all the code context

text Etc that you're going to need to be

successful in this video and I'm going

to be referring to it pretty often as we

go through the course additionally in

this GitHub there's a discussions tab

right here that you can click on and in

here is where you can ask questions

discuss with other people taking the

course interact with members helping out

and it's where you can discuss anything

that you're having trouble with and an

important note sometimes you'll see this

as the chain Excel org Foundry F course

we recently renamed it to The cyphon

Foundry F course so this is the correct

link but if you see chain excl org

that's fine as well that being said as

we go through this course we're also

going to teach you some best practices

on working with artificial intelligence

how to best prompt these AI so that they

can give you the best results just keep

in mind they sometimes get things wrong

and it's a good idea if you are going to

use an AI to fact check it with a human

or another resource so be sure to say hi

in the discussions and maybe meet some

like-minded peers and additionally once

we do get to the coding portion of this

course it's a good idea to code along

with me as I'm explaining things so

having the video up as well as your

coding screen is a good idea so you can

follow along with me as I'm explaining

it now this space moves incredibly

quickly so whenever I open some

documentation or some codebase or

something I highly recommend that you

open it as well in your browser just so

that you can know immediately right away

that the code that I'm working with in

the video is going to be the same that

the code that you're working with

locally now we're going to be keeping

all of the code in here up to date but

sometimes things change and something

that I do in the video might not be the

most up to- dat best practice so we're

going to have this file called

chronological updates. MD where you can

go in and check to make sure that you're

working on the most upto-date Edition so

if you go into that file each lesson

will have a section and if there's some

update that we made to the lesson you

can find it in there additionally if you

think you found something that is

different or doesn't quite work be sure

to make a discussion for it in that

GitHub repo like I said it's going to be

your Bible but yes if you run into an

issue make sure that file is one of the

first places that you check just to make

sure that all the code that you're

working with is the most up to dat all

of this is to say if you run into an

issue jump to that GitHub repo and make

a discussion we will also be giving you

some tips very soon about how to best

make a discussion yes asking questions

to other human beings is a skill and

we're going to try to teach you to be

the most effective because asking well

formatted questions is not only the

secret to being a fantastic AI prompt

engineer but also becoming an incredibly

successful developer we're going to

learn how to ask well-formatted

questions and whenever we post on

discussions or forums or whatever we're

going to work on formatting them as best

as possible take breaks I cannot tell

you how many people have tried to rush

through these courses and be like Oh I'm

going to finish in a single weekend your

brain doesn't work like that your brain

needs time to absorb the information so

take breaks maybe every 25 minutes to a

half hour take a 5-minute break or maybe

you like working in longer chunks Maybe

take a whole hour and then take a 15 20

minute break don't try to rush through

the whole video in a day you're not

going to retain the information go

outside go for a walk grab some ice

cream get some coffee go to the gym your

brain needs time to have the information

settled maybe every 2 hours just step

away maybe be done for the day work at

whatever Pace makes sense for you

everyone's going to have a different

learning Pace there is no right speed

for this course I've had people take my

courses in 2 weeks in 3 months in six

months months it doesn't matter pick a

pace that you can do and stick to it not

only work at your pace make sure that

I'm talking at a pace that makes sense

for you there's a little gear icon in

the YouTube video here where you can

change the speed of how I'm talking and

how fast the video is going so if I'm

talking way too fast for you then you

can slow me down but if I'm talking too

slow then you can speed me up so make

the adjustments you need to make me go

the speed you want me to go now a giant

video like this can be kind of hard to

to triage where you left off so using

the GitHub repo with the timestamps in

there is a good way to say ah okay I was

on lesson one let's click the link there

to jump right to the timestamp if you

pause a video in YouTube you can

actually rightclick and say copy at

current time and maybe drop that into a

notes folder somewhere so that you can

always just pick right back up where you

left off or like I said you can use some

of the timestamps in the GitHub repo

associated with this course or depending

on when you watch this the web3

education. site might also be up be sure

to check that out as well and of course

this course is modular so you can Bounce

Around topic to topic and go to where

you want to go if you don't want to do

any full stack stuff then skip that

section if you want to go right to the

advanced stuff do that like I said go

the pace and take the learnings that you

want to do and after every lesson it

might be a good idea to go back and

reflect on each lesson to really make

sure the knowledge gets ingrained

repetition is the mother of skill and

we're going to be repeating a lot of

smart contract development now

additionally at the end of every lesson

you'll see a little QR code that looks

something like this and there will be a

link in the GitHub repo pointing to the

same place that this QR code is pointing

to these are optional challenges that

you can do to try to make sure that you

actually learned what was meant to be

learned here and if you do solve them

you get a very cool nft along with it

don't know what an nft is don't worry

we'll teach you later blockchain

development and open source development

world is incredibly collaborative so be

sure to use tools like of course the

GitHub discussions tab ethereum stack

exchange the decentralized Q&A Forum

piranha issues on different

to unblock yourself on this and really

anything in life plus sinking with other

people in the space makes it way more

fun now before we can actually get to

coding we need to understand how the

blockchain even works what the purpose

of these smart contracts even are and

this is essential to becoming a

successful smart contract developer

because a technology is really just a

solution and a solution is only as good

as the problem is so we need to make

sure we understand the problem really

well so we know how to attack it with

this smart contract technology and the

better you understand this smart cont

technology the better you'll be able to

architect your smart contracts in the

future and make really intelligent

really powerful systems that further

this amazing industry but if you already

know the basics of blockchain feel free

to jump into lesson two and skip over

lesson one so those are some of the best

practices to be really successful with

this course but with that knowledge

you're now standing at the edge of the

rabbit hole and if you're like me once

you jump in you'll just want to keep

going deeper and and deeper I'm so

excited for you to embark on this

journey with us and I'm looking forward

to seeing you on the other side just

like the thousands of other developers

who have taken these courses and have

emerged the other side triumphant so it

all starts with blockchain Basics let's

get

froggy now since you're here you've

probably heard heard of Bitcoin before

Bitcoin was one of the first protocols

to use this revolutionary technology

called blockchain the Bitcoin white

paper was created by the pseudo

Anonymous Satoshi Nakamoto and it

outlined how Bitcoin could make

peer-to-peer transactions in a

decentralized network this network was

powered by cryptography and decentral

and allowed people to engage in

censorship resistant Finance in a

decentralized manner due to its features

which we'll talk about in a little bit

people took to this as a Superior

digital store of value a better store of

value over something like gold for

example and that's why you'll also hear

people commonly refer to it as a digital

gold similar to Gold there's a scarce

amount or a set amount of Bitcoin

available on the planet only so much

that you can buy and sell you can read

more about the original Vision in the

white paper we have a link to the white

paper in the GitHub repo associated with

this course now this was an insane

breakthrough and in a little bit we're

going to learn exactly how this is all

possible and how this actually works

under the hood some people though saw

this technology and wanted to take it a

little bit farther and do even more with

this blockchain technology and a few

years later a man named vitalic butterin

released a white paper for a new

protocol named ethereum which used this

same blockchain infrastructure with an

additional feature and in 2015 him and a

number of other co-founders released the

project ethereum where people could not

only make decentralized transactions but

decentralized agreements decentralized

organizations and all these other ways

to interact with each other without a

centralized intermediary or centralized

governing Force basically their idea was

to take this thing that made Bitcoin so

great and add decentralized agreements

to it or smart contracts and in fact

technically these smart contracts

weren't even really a new idea back in

1994 a man named Nick Zabo had actually

originally come up with the idea smart

contracts are a set of instructions

executed in a decentralized autonomous

way without the need for a third party

or centralized body to run them and they

come to life on these blockchains or

these smart contract platforms like

ethereum and it's these smart contracts

that are going to be the core thing that

we're going to be working on in this

course and that we're going to be

developing you can think of smart

contracts in the same way you think of

traditional contracts or traditional

agreements they're just a set of

instructions between parties except

instead of written on pen and paper or

typed up in Microsoft Word they are

written in code code and embodied on

these decentralized blockchain platforms

and that's also where they're executed

instead of being executed by the two

parties or three parties or however many

parties that are involved this removes

this centralized issue that we'll talk

about more in a bit this is one of the

main differentiators between the

ethereum protocol and the Bitcoin

protocol it's these smart contracts now

technically Bitcoin does have Smart

contracts but they're intentionally

touring incomplete which means they

don't have all the functionality that a

programming language would give them

this was an intentional move by Bitcoin

developers Bitcoin developers viewed

Bitcoin as a store of value versus

etherum developers viewed ethereum as

both a store of value and a utility to

facilitate these decentralized

agreements now these smart contracts on

blockchains alone are absolutely

incredible however they do come with a

huge issue if we want these digital

agreements to replace the agreements in

our everyday lives they probably are

going to need data from The Real World

blockchains by themselves actually can't

interact with and can't read or listen

to data from The Real World this is

what's known as the Oracle problem these

blockchains are deterministic systems

and they're deterministic on purpose and

we'll learn about more about how that

works in the sessions to come so

everything that happens with them

happens in their little world but if

they're going to be these agreements

they need external data and they need

external computation and this is where

oracles come into play oracles are any

device that delivers data to these

decentralized blockchain or runs

external computation however if we want

our applications to stay truly

decentralized we can't work with a

single Oracle or a single data provider

or a single Source that's running these

external computations so we need a

decentralized Oracle Network similar to

our decentralized blockchain Network

your onchain logic will be decentralized

but you also need your offchain data and

computation to be decentralized

combining this onchain decentralized

logic with this offchain decentralized

data and decentralized computation gives

rise to something called hybrid smart

contracts and most of the biggest

protocols that we interact with today

are some type of hybrid smart contract

or interact with hybrid smart contracts

to some extent this is where the

protocol chainlink comes into play it is

a modular decentralized Oracle Network

that can both bring external data and

external computation into our smart

contracts to make sure they're

decentralized end to endend while giving

them the feature richness that we need

for our agreements chain link allows for

us to get data do upkeeps get random

numbers or really customize our smart

contracts in any meaningful way now

throughout the course we're going to use

the terminology smart contract however

whenever we say smart contract we're

often using it a little interchangeably

with hybrid smart contracts but just

know that when we say hybrid smart

contract we're talking specifically

about smart contracts that have some

type of offchain component now since

ethereum's release a number of different

blockchains or smart contract platforms

have come to light such as Avalanche

polygon Phantom Harmony and more for the

majority of this course we're going to

be assuming that we're going to be

deploying to the ethereum network

however everything that we learn here is

going to be applicable to the vast

majority of the blockchains out there

like polygon Avalanche Phantom Harmony

Etc and understanding everything from

ethereum fundamentals will give you the

skills that you need to switch chains

very easily with literally one line of

code so don't worry about learning a

specific tool or with a specific change

because most of them work together

seamlessly now there are a couple of

smart contract platforms that don't use

solidity but still learning the

fundamentals here will make you much

better at those as well and ethereum by

far has the most value locked and is the

most used blockchain and smart contract

platform out there you'll also hear

those two terms used a little bit

interchangeably as well sometimes I'll

say smart contract platform sometimes

I'll say blockchain they kind of mean

the same thing obviously blockchains

could mean store of value and smart

contract platform but you get the idea

similarly chain link is the most popular

and Powerful decentralized Oracle

network is the one that we're going to

be focusing on for this course as well

chain link is also blockchain agnostic

so it'll work on ethereum Avalanche

polygon salana or really any other

blockchain out there now additionally

over the last year a new term has come

to light called an L2 or a layer 2 this

solves an issue that most blockchains

see where they don't scale very well or

they don't grow big very well we'll be

talking about l2s a little bit more in

the future but the basic concept of is

that blockchains can really only get so

big so what they do if if this is

ethereum you can actually have

blockchains hook into them to

essentially make them bigger if that

doesn't really make too much sense don't

worry about it for right now layer twos

solve this scalability issues and at the

moment there are two different types of

true layer tws optimistic Roll-Ups and

zero knowledge Roll-Ups optimistic

rollups like arbitr and optimism or zero

knowledge roll-ups like ZK sync or

polygon ZK evm yes there's a polycon

chain but there's also a polycon ZK evm

L2 the two of them are very different

don't worry about them for now and in

fact it's this arbitrum layer two where

our challenge contracts are going to be

deployed on this rollup but like I said

once we learn how blockchains work from

a basic Level under the hood then we'll

explain more about how these l2s

actually work now throughout this course

you'll hear the term dap or

decentralized protocol or smart contract

protocol or decentralized application

and they all kind of mean the same thing

a decentralized application is usually

the combination of many smart contracts

and when we get into solidity you'll see

what a singular smart contract really

looks like and like I said learning all

these core fundamentals will make you a

better solidity and a better smart

contract developer you'll also hear the

term web 3 a lot in this video and in

the industry web 3 is the idea that

blockchains and smart contracts are the

next iteration of the web web one being

this permissionless open- Source world

with static content web 2 being the

permissioned web with Dynamic content

but all the agreements and logic runs

off of centralized servers where they

control your information and then web 3

comes back to the permissionless web but

once again with Dynamic content and

instead of centralized servers running

your logic decentralized networks run

the logic creating these censorship

resistant agreements that these smart

contracts enable it is also generally

accompanied by the idea that the users

own the protocol that they work with and

it's an ownership economy you'll see

what I mean later in this course now

we've talked a lot about the history and

about the high level of these protocols

and of these smart contracts and what

they can do but what do these smart

contracts really mean what is it when I

say trust minimized agreements or

unbreakable promises what is the real

value ad of these smart contracts before

we look under the hood and take a peek

at how this all works from a technical

standpoint let's learn what all the

value of this is what is the purpose of

of us building all these Technologies of

you taking this course what problem does

this technology solve in my mind a

technology is really only as good as the

problem that it solves if it doesn't

solve a problem then why bother smart

contracts blockchain web 3

cryptocurrencies those are all just

different words that encapsulate the

idea of what we're doing in such a

unique Paradigm I think the easiest way

to sum up what these smart contracts do

is that they create trust minimized

agreements and if you might be

scratching your head to that a much

easier way to think about it is just

they give rise to Unbreakable promises

Yes you heard that right unbreakable

agreements and Promises additionally

they give rise to speed efficiency and

transparency and a number of other

things I made a video pretty recently

about exactly this so let's dive in and

take a listen to the purpose the

undeniable value of smart

contracts cryptocurrencies fundamentally

Rel landscape Market markets and

agreements as we know them unfortunately

you've probably only been bombarded with

people screaming about nfts and money

now some of the memes are fun but let's

forget the and get down to the

essence of this space if you're already

in web 3 this is the video to send to

your friends to explain why you're so

excited about this space and explain why

we're here and then if you're not into

crypto you've come to the right place

and yes there are fun memes and markets

and there's some money stuff and there

all these things but outside of all that

the purpose of blockchains relates to

the age old old elementary school

unbreakable promise the pinky swear

let's get

froggy nearly everything you do in life

is the result of an agreement or a

contract your chair was the result of an

agreement to buy and sell lumber to

assemble and sell the chair to a

retailer on Amazon then you made an

agreement to buy the chair for $40 the

lights in your house are powered by

electricity which is an agreement from

you and the electric company you agree

to pay them in return they'll keep the

lights on the electricity that they

generate is agreements between them and

Engineers who built turbines to generate

the electricity with insurance you agree

to pay some amount of money to them

every month and in return they will do

nothing or I mean they'll cover your

medical bills almost everything you do

and everything you interact with is the

result of some form of agreement or

contract in some aspect now agreements

and contracts can feel kind of abstract

and boring to really grasp on to so to

simplify we can also refer to them as

promises when you get an oil change

they're promising that they will

Faithfully change your oil in exchange

for money when you put money in the bank

they promised to keep it safe in

exchange for them to use your money to

give out loans when you buy a lottery

ticket the lottery promises to give you

a fair chance at winning a ton of money

in exchange for you buying the ticket

whenever you make one of these

agreements in a way you're asking them

to pinky swear to not screw you over and

to treat you fairly but this doesn't

always happen let's look at a real world

example of someone breaking the pinky

swear back in the ' 80s and '90s

McDonald's ran a promotion for people to

win money by collecting McDonald's

Monopoly game cards the idea was simple

you buy McDonald's in return you get a

chance to win $1

million you can imagine McDonald's

literally going hey everybody I promise

if you buy our MC food and McNuggets

we'll give you a fair chance of winning

this

money but they ended up breaking This

Promise instead of having a fair chance

of winning your chance was in fact zero

in the mid90s between 13 and $24 million

went into the pockets of not people

playing the game honestly but a group of

corrupt insiders who had rigged the game

meaning that when you played the

McDonald's Monopoly game you were buying

into a set of lies and promises that

were 100% always going to be broken and

the thing is it doesn't really matter if

this was McDonald's fault or not they

were the ones making the promises that

they ultimately could not keep another

way you can think about it is that

that's $24 million that they essentially

stole from you and I now if this system

was deployed on a blockchain with

something called a smart contract it

would have been impossible to defraud

this $24 million due to Smart contracts

being a mutable decentralized and

transparent but I'll get back to that in

a

minute in all the agreements and

contracts we make imagine making a pinky

swear with a 10-year-old and imagining

how that agreement would hold up hey

buddy could you could you please keep my

money safe you can play with it if you

like but just just please have it when I

come back immediately you might get that

worrying feeling in your chest something

might go wrong that this 10-year-old

might lose your money you might be

thinking how could I trust them will

they break their promise and this

feeling of I can't breathe because of

untrustworthy situations happens to us

all the time can I trust this used car

salesperson to give me a good car can I

trust this tag that says machine

washable or will it make my shirt shrink

will my insurance provider break their

promise of covering my medical bills

when I get hit by a bus when Patrick

promises he'll go on a hike with me will

he actually yes I I I actually will the

issue with our current agreements and

contracts is we have to trust the people

who are making them to do the right

thing however often they're actually

incentivized to not do the right thing

insurance doesn't want to pay out money

sometimes salese just want to get the

off their shelves and with my

girlfriend I promised to go on a hike

but I hate hikes where else has this

happened now you might be thinking okay

Patrick this seems cool but like where

has this actually affected me well the

McDonald's Lottery that we just spoke

about above during the Great Depression

with the run of the banks Banks promised

to keep our money safe and that when we

went back to go get it they would

actually have the money there and well

and behold there were times that they

didn't have the money there just last

year Robin Hood painted this amazing

picture come use our application we will

give you access to the markets we

promise we will give you a retail

investor a fair chance of interacting

with the world of

Finance Psy but not this asset this

asset this asset or this asset the 2008

financial crisis remember that shady

deals behind closed doors combined with

lies about financial product brought the

world to its economic knees how are you

us hyperinflation in Zimbabwe

hyperinflation in Brazil fair enough

history is a Relentless lesson of

trustworthy entities being notorious

promise Breakers we finally have a way

to fix it with smart contracts now

before I jump into smart contracts a lot

of people might be thinking hey cool and

all however we have systems in place to

protect against a lot of these things

which is is true and which is great and

that is a very helpful step forward but

these systems often break ones in 2008

definitely didn't work the ones with the

Robin Hood crisis definitely didn't work

and even if these systems apply and you

go to court to try to work them out

maybe you're in court for years before

you actually see a resolution and by

that time what you needed the money for

is long gone so what is this technology

what is this tool that can fix this

fundamental problem in our agreements

today this tool is smart contracts and

this tool is what the blockchain was

built for now I'm going to give you a

quick overview of what a smart contract

is however I'm leaving some links in the

description for more in-depth

explanations but the basics of them is a

smart contract is an agreement contract

or a set of instructions deployed on a

decentralized blockchain and once the

contract or set of instructions is

deployed it cannot be altered it

automatically executes and everyone can

see the terms of the agreement the real

basics of it is that the code is

executed by decentralized Collective

like a group of people but a group of

people running a certain software this

means that no one person or entity can

actually alter any of these agreements

or change the terms of the arrangement

in these traditional agreements whoever

owns the contract whoever owns the

execution of the contract can flip a

switch and say n we're not going to do

that anymore in smart contracts in web 3

in blockchain you no longer can do that

typically these smart contracts are in a

decentralized blockchain and used in

combination with a decentralized Oracle

Network to get the real world assets and

information and if these words sound

like I'm Conjuring up a magic spell well

again check the links in the description

if you want to learn more about the

technical implications if you're not a

technical person and you're not

interested in getting to the Integrity

you can kind of think of it like https I

bet the vast majority of you don't even

know what https stands for and yet you

use it every single day whenever you log

onto the internet so how does this fix

the McDonald's Monopoly issue in its

traditional form the lottery was

executed behind closed doors somebody

operated and owned the code and the

contracts and the agreements that ran

the lottery and they had the power to

alter it and nobody other than the

people internal on the lottery could

audit this altering happening now if the

code for this Lottery was deployed onto

a blockchain every time a hacker

attempted to alter it everyone would be

notified not only that but you couldn't

even alter it because the terms of a

smart contract cannot be altered once

deployed combine that smart contract

with a chain link vrf Oracle to get a

verifiably random number and Presto you

now have a perfectly decentralized

unalterable agreement that is impossible

to hack commit fraud or manipulate we

have just saved the public between 13

million and $24 million just by fixing

the issue of trust how does this fix

Robin Hood well the problem with Robin

Hood is already fixed right again the

problem is that there's a centralized

body that can flip a switch at any time

and say yeah you can't access these

markets anymore we're breaking our

promise of actually giving you access to

the markets this is already fixed with

something called decentralized exchanges

and these exist today one of these

exchanges is one called Unis swap you

can swap erc20 tokens which are kind of

the equivalent of stocks but some aren't

some are it's a little confusing I won't

get into that here either but it doesn't

have that centralized body that can flip

a switch and ruin access to the markets

and had these investors been on a

decentralized exchange it would have

saved them hundreds of millions of

dollars and it would have prevented

fraudulent Market manipulation how does

it fix run of the banks with

transparency built in and automated

solvency checks you can build a bank

like smart contract that has insolvency

checks built in that make it impossible

to get there insolvent means broke as

any agreement or any history lesson

where there was a trust assumption that

was broken smart contracts can be

applied to and should be applied to

especially in a time where big money

runs owns and controls everything we

desperately need to move to a world

where some self-interested centralized

entity can't flip us switch and ruin

people's access to the services that

they need we can move away from a world

that is brand-based to a world that is

math-based right now if you interact

with a service that you don't like or

that they break their promise the only

thing you can do is walk down the street

to the next service that's going to make

the same set of promises and you have to

hope and pray that they're actually

going to keep it we can move from that

to a world where we can just look at the

math and say oh okay 1+ 1 equal 2 this

is what this agreement is going to do

for me every single time guaranteed

because it's a decentralized autonomous

agent has no incentive to be evil and

everything is transparent and out in the

open I'm a big company and if it was

better for me for 1+ 1 to equal three

maybe I would go behind some closed

doors and fudge some numbers and come

back out and be like hey 1+ 1 equals 3

but with smart contracts that's

impossible doing the right thing is

infrastructural now given the choice

between two agreements one where you

have to trust a single centralized

entity that they're going to do the

right thing for you versus a

decentralized untable collective which

one are you going to choose I'm picking

the one that can't screw me over every

single time for every agreement I can

apply it to now this technology is

relatively new but we have already seen

it Rel landscape entire markets and

continue to do so the traditional

Financial world is already getting its

lunch eaten by defy or decentralized

Finance there's already over $200

billion of people's money in these

protocols to help have a more fair more

accountable more transparent Financial

system this D5 movement is one of the

main reasons I got into this space

because we desperately need to move away

from where we are right now and end

people's chances for wealth being sucked

up by some group that's bending the

rules in their favor and smart contracts

are a ticket to that better World more

and more Industries are also coming over

to Smart contracts and blockchain

because of all the Innovations and

because of all the advantages that it

has as we grow and as we get better we

we get closer to this vision of having

this concept fulfilled trust minimized

agreements these smart contracts are

minimizing the trust that we need to

give other people in order for these

agreements to be executed if trust

minimized agreements is too confusing

for you just say unbreakable promises

now I got to be honest with you guys

blockchains and smart contracts and

cryptocurrencies can actually do more

than just trust minimized agreements

what they have Security benefits uptime

benefits execution speed benefits and a

whole lot more but it's a lot easier to

just learn about one and learn the other

ones later right it's kind of like

sprinkles on top so this is why we are

here this is why we're building this

future and this is why we are so excited

about

it last year 2022 there were a lot of

issues with a couple different companies

like for example spf's FTX platform the

thing to me that's most frustrating

about that situation is that FTX

platform wasn't anything that I just

talked about it wasn't decentralized it

wasn't trustless it wasn't transparent

it was purely a traditional web 2

company pretending to be web 3 and just

using the cryptocurrency part of web 3

but not actually using the smart

contracts and we're doing a much better

job as a community getting rid of the

Bad actors and this is something that's

incredibly important for you when

working with protocols and when building

protocols I want you to be incredibly

successful here but I want you to be

incredibly successful because you're

making a ton of value a lot of these

platforms that we saw collapsing last

year were not creating value they were

stealing value they were siphoning value

they were faking having value and as you

learn and as you build smart contracts

yourself it'll start to become innately

aware of what protocols and what

companies are centralized and are not

the ethos of web 3 and the ones that are

we are building verifiable trust

minimized agreements unbreakable

promises and if you can't verify those

promises then it's not trust minimized

it's not web 3 it's not what this

industry is for that's what I want you

to do as you finish this course is be a

force for good unfortunately because a

lot of people haven't taken my course

not everybody understands the difference

between a legitimate project and a token

that's just meant to pump somebody's

bags as this space continues to grow and

as people like yourself take courses

like this we will get to continue to

push real legitimate projects forward

and wash out the projects that aren't

actually contributing to web

3 even in just this introduction part

we've learned a ton so let's do a quick

summary of what we've learned so far

Bitcoin was the first protocol to take

this blockchain technology into the

Limelight and take these

cryptocurrencies into the mainstream

Bitcoin is a sort of digital gold or a

store of value able to make transactions

between users in a decentralized manner

ethereum and other smart contract

platforms take this blockchain

technology one step further enabling

people to make smart contracts in

decentralized trust minimized agreements

these smart contracts and decentralized

applications can access an inter

interact with the real world using

something called decentralized Oracle

networks chain link is a decentralized

network that allows us to build these

hybrid smart contracts which combines

our onchain logic with our offchain

decentralized data and decentralized

computation giving rise to our logic

being completely decentralized and our

data and external computation being

completely decentralized giving us all

the features that traditional agreements

and traditional contracts have now these

digital currencies like ethereum and

Bitcoin have value even without the

smart contract part having a censorship

resistant decentralized store of value

is immeasurably powerful in its own

right we have some links in the GitHub

repository that'll teach you how this

decentralized store value flips

traditional Finance on its head and it's

another one of the great reasons for

building smart contracts but again the

easiest way to boil it down is trust

minimized agreements or unbreakable

promises but let's also go into some of

these other features that smart

contracts have over our traditional

environment the first feature of course

is that they are decentralized and they

have no centralized intermediary the

different individuals that run one of

these blockchains are known as node

operators and it's the combination of

all these thousands of node operators

running the same software running these

algorithms running these smart contracts

that make the network decentralized

we'll dive deeper into how that works

later the next feature is transparency

and flexibility in these decentralized

networks since all these individual node

operators run this software everybody

can see everything that's happening on

chain meaning there's no Shady deals

there's no weird things happening

anything that's going to be unfair

people would be able to see and just not

use everybody has perfect information

and has to play by the same rules now

additionally this doesn't mean that

there's no privacy the blockchain is

pseudo Anonymous meaning that you aren't

necessarily tied to an identity in real

life they also have the feature of speed

and efficiency for those of you who have

ever tried to do a bank transfer or send

money across Seas you know it sometimes

can take 2 to 3 weeks when in fact all

these banks are really doing is basic

math they're subtracting money from your

balance and adding it to some other

balance why does it take so long in the

blockchain all of these transactions

happen instantly another instance for

those in the financial world today know

that clearing houses and settlement days

can take a long time in the blockchain

there's no need for any of that because

they happen instantly this obviously is

much quicker but it also makes for much

more efficient interactions with each

other security and immutability again

immutable means that it can't be changed

once a smart contract is deployed that's

it whatever is in the code is going to

be in the code Forever they cannot be

altered or tampered with in any way this

means that the security is much easier

whereas in a centralized World somebody

can hack into the server jump out the

database and change some numbers you

can't do that in the blockchain world

and since it's decentralized in order to

hack the blockchain you you'd have to

take over half of the nodes as opposed

to in the centralized world where you

only have to take over one in the

regular world if your computer and your

backup computer go down all of your data

is gone in the blockchain world if your

computer and your backup computer go

down all your data is safe because it's

being run on all these other

decentralized nodes and even if a few

hundred nodes or if a few thousand nodes

go down it doesn't matter because as

long as one node has a copy of the

blockchain you're good to go hacking a

blockchain is nearly impossible and

Leaps and Bounds more difficult than

hacking a centralized server not only

that but this is safer in the asset

sense as well all you need to access

your credentials and your information

and your assets is your private key

which is basically your password for all

of this and as we've discussed in the

video these smart contracts remove this

counterparty risk remove this

centralized intermediary remove these

trust gateways that we have to do in web

2 when we engage with users and

individuals they don't always have our

best interests at heart smart contracts

remove this counterparty risk because

once one of these contracts is created

they can't go in and they can't alter it

and they can't let greed or ego or

anything else get the better of them and

alter the terms of the deal and as we

said this gives rise to these trust

minimized agreements or these

programmatic unbreakable promises we

move away from brand-based agreements to

math-based agreements where we can look

at the cryptography we can look right at

the code and see exactly what something

is going to do and how it's going to

execute versus having to rely on a human

being doing the right thing with smart

contracts and decentralized hybrid smart

contracts doing the right thing is

infrastructural all these pieces boil

down to us having the freedom to

interact the way we want to interact

without having to be afraid that

interacting like that is going to screw

us over this trust minimize peace these

unbreakable promises make interactions

so much better in the purely to World

we're constantly bombarded with messages

of projects and protocols pushing us to

move or act in the direction that makes

them more profitable versus in the smart

contract space we can see everything

transparently and we can even engage and

interact and be partially owners of the

protocols and the interactions that we

decide that we want to be a part

of so smart contracts have been around

for a few years now and what have they

generated for what industries have come

about due to these smart contract

platforms being around well you've

probably heard of some of these and some

of these we've already mentioned but

let's give you a quick refresher defi

defi stands for decentralized finance

and it gives users the ability to engage

with finance and markets without having

to go through a centralized intermediary

for example like we said with Robin Hood

you'd no longer have to trust that Robin

Hood would continue to give you access

to the markets you instead would be able

to see in the smart contract yes I have

access to the markets or in the 2008

financial crisis you never have to trust

that these groups and institutions are

giving you the correct things on the

back end you can see everything

transparently right on the blockchain

you can engage with things like money

markets and sophisticated Financial

products easy effectively and securely

if you're really excited about defi we

have a ton of defi examples showing you

how to build and interact with these

protocols in coming lessons Dows or

decentralized autonomous organizations

are another group that we've already

mentioned Dows are groups that are

governed completely centralized by a set

of instructions or smart contracts on

chain there are some massive benefits

here where engagement is much easier the

rules are black and white and you can

see everything directly on chain voting

and governance technology is completely

decentralized and the blockchain space

is one of the big ones pushing how we

can evolve politics and how we can

evolve governance to make it more

efficient fair and reasonable and you

better know it we have some examples of

how to build Dows and how to work with

Dows in coming lessons so be sure to

watch those nfts stand for non-fungible

tokens and can really be kind of

described as digital art or just a

unique asset they can do so much more

but we'll keep it high level for now

projects like board apes and crypt punks

have revolutionized the way that people

get paid for their work show off their

creativity status and so much more and

yes of course we have lessons showing

you how to create and interact with nfts

as well so many other groups and so many

other Industries are being created as a

result of this insane technology and

maybe after finishing the journey with

us here you go out and you'll be the one

to Pioneer the next industry or the next

billion dooll idea you've learned so

much already but now that we've learned

a lot of this highlevel information

let's finally jump in and let's make

your first transaction and let's get you

set up to interact with this new world

in this next section we're going to get

you a wallet and we're going to show you

exactly what a transaction looks like

and feels like let's dive

in this is the ethereum website

ethereum.org we are going to make a

transaction on a test ethereum

blockchain I'll explain what that means

in a little bit this is going to be our

first ever transaction that's made on

the blockchain and this process of

making a transaction is going to work

the exact same across all evm compatible

blockchains and layer 2s like arbitrum

ethereum ZK sync and Etc I'll explain

what evm means in the future for now

just follow along and have fun running

your first transaction now in order for

us to send a transaction on any of these

evm chains the first thing that we need

to do is set up a wallet so I'm going to

go to metamask because it's one of the

most popular wallets and one of the

easiest wallets to use I'm using the

brave browser but it works for Chrome or

Firefox or really any other popular

browsers out there and it's just going

to be an extension in the top right hand

of our browser it's going to make it

very easy to see anything to do with our

wallets and our transactions very easily

and it's going to store all of our evm

based currencies and evm based

transactions so I'm going to go ahead

and hit add to Brave ADD extension

although Brave does also come jam-packed

with its own wallet so now we come to

the get started page and I'm going to go

ahead and select create a new wallet

sure we'll agree to help out metamask

now we're going to create our password

make sure it's really secure for the

purpose of this demo mine's going to be

kind of mediocre now I'm going to

preface it

this wallet that you're making right now

as you follow along with me this is

going to be your development wallet so

if you want to make the password a

little bit weak just so that you can

test things out very quickly go for it

just know we're never ever going to put

real money into this wallet it's good if

you treat this as if it is a real wallet

that way you'll get used to and you'll

get familiar with good wallet safety you

will then get a video like this which

will teach you about the secret recovery

phrase which we saw a little bit earlier

when we were creating our wet let's

watch this video metamask is a new way

to connect to sites and applications on

traditional websites a central database

or bank is responsible for controlling

and recovering your accounts but on

metamask all of the Power belongs to the

holder of a master key whoever holds the

key controls the accounts your secret

recovery phrase is your master key it's

a series of 12 words that are generated

when you first set up metamask which

allow you to recover your wallet and

funds if you ever lose ACC access it's

important that you secure your wallet by

keeping your secret recovery phrase very

safe and very secret if anyone gets

access to it they will have the master

key to your wallet and can freely access

and take all of your funds to secure

your metamask wallet you'll want to

safely save your secret recovery phrase

you can write it down hide it somewhere

put it in a safe deposit box or use a

secure password manager some users even

engrave their phrase onto a metal plate

nobody not even the team at metamask can

help you recover your wallet if you lose

your secret recovery phrase if you

haven't written down your secret

recovery phrase and stored it somewhere

safe do it now we'll wait and remember

never share your secret recovery phrase

with anyone not even us if anyone ever

asks you for it they're trying to scam

you that's it now you know what a secret

recovery phrase is and how to keep your

wallet safe and secure awesome so that

was a great introduction to keeping your

wallet safe we'll talk a little bit more

about safety with our wallets in the

future let's go ahead and select secure

my wallet now this is where we need to

write down our secret recovery phrase

and save it in a very secure place it

gives us some tips here like a password

manager a safety deposit box or split it

up and keep it in multiple secret places

for the purposes of this video I'm going

to be showing you the secret recovery

phrase because I'm not going to put any

real money into this but you should

never never ever do this additionally

you'll sometimes hear pneumonic as a

synonym for secret recovery phrase the

main takeaway from all this is you

should never share any of this this is

for you only if you show this secret

phrase to anybody else they will have

access to not just one account but every

account that you make in metamask so be

absolutely certain to not share this

with anybody so again I know I'm

belaboring the point a little bit but

everything that we're going to do in

this tutorial we're going to do with

fake money and fake make assets and

never put actual money into this account

that we're making here once you get

familiar with using metamask and working

with the tools and stank secure then you

can go ahead and create a separate

metamask that will have real funds in it

if you want to put real money in

different metamask a lot of browsers

have a profile option and maybe you can

make a new profile install metamask on

that different profile call that profile

real money profile or something and

that's where you will store your money

but for this video for this tutorial the

mamass that you are using is going to be

specifically for are testing things out

and you will never store real money to

it I'm going to harp on that a lot more

in this course so even if you're coming

here and you have a wallet I highly

recommend still making a brand new one

for this tutorial just in case you don't

accidentally code something or do

something atomous and give away your

funds if this is your first wallet then

great but again when you're working with

real money if you lose access to the

secret phrase you will lose access to

all your money so be sure to write this

down promise me that you won't use real

money for this course great I'm going to

hit copy to clipboard for now and we're

going to go ahead and hit next now we

need to confirm by adding our seed

phrase back in we can go ahead and hit

confirm and we now have created our

wallet let's go ahead and clict got it

awesome now we can see the interface of

our metamask full screen and depending

on your browser what you can normally do

is hit this little puzzle piece on your

browser and select this pin button so

now we can pin our metamask into the top

of our browser and we can click it like

so

and we can see it give a little drop

down like this and we can see the same

information in this little drop down as

there is on the full screen now even if

you lose access to that page now that

this is bookmarked in your browser you

can select your metamask select these

three dots and hit expand view to reach

this tab now additionally what we can do

in here is we can actually go up to our

accounts and we can actually create

multiple accounts by hitting create

account and if you wanted to you could

give it a name here I'm just going to

leave it as default for account two and

now we have two separate accounts we

have an account zero with an address and

an account two with an address as well

both of these accounts actually share

that same secret phrase so anybody with

access to the secret phrase can actually

have access to both accounts however

they have different private keys and

that's what makes them different we'll

talk a little bit more about that in the

future if somebody gets access to a

private key they'll get access to a

single account if they get access access

to the secret phrase they'll get access

to all the accounts that you make even

you know if you made a third one they'd

get access to this one as well now if

you look up in the top right of the

screen here you'll see this section that

says ethereum mainnet this is our

networks Tab and if you click it you can

see all the different networks that our

metamask has access to ethereum mainnet

is the main network of ethereum and this

is where real money is spent and used

for this course we're not going to be

working with ethereum mainnet we're

instead going to be working with

something called a test net for both

engineers and non-engineers we often

need a place to test or simulate our

transactions and for the developers here

throughout this course we are going to

teach you another technique for testing

out your transactions on a local network

and a local network is actually going to

be the preferred way we do our testing

and our simulations however it's still

really important to see end to end what

a real transaction looks like and that's

what a test net will do for us it

simulates exactly what a mainnet or a

live money Network would look like

however there's no real money at stake

and we don't actually have to spend any

money to see some of the test Nets that

come default with metamask we can hit

the show/hide button which will bring us

to the settings page of metamask we can

turn on show test networks and if we

scroll back up now if we hit our

networks tab actually let's go ahead

close out of settings now if we hit this

drop down we can see gelli test Network

sapoia test Network and Linea gorelli

test Network these Networks networks are

test networks that resemble ethereum or

polygon or Linea or arbitrum or optimism

or ZK sync or any other evm compatible

chain that we want to work with and

again we'll Define evm in the future and

we can actually switch the network that

we're working on simply by clicking

another Network so let's switch to

sapoia we can see our Network changed up

here and now we can see we have zero SEO

eth so on eth mainnet this new account

has zero ethereum and on the sapoia test

Network we also have zero sapoia eth

which makes sense because this is a

brand new wallet and we haven't put any

money into this brand new account yet so

of course we have zero at the time of

recording sapoia is one of the most

popular test networks out there so we're

going to be working mainly with sapoia

throughout this course however test Nets

often change because again they're run

out of the goodness of people's hearts

and sometimes people stop running them

you should absolutely have either the

web3 dev. education site up or the

GitHub reposit associated with this

course and an important note sometimes

you'll see this as the chain Excel org

Foundry FL course we recently renamed it

to The cyphon Foundry F course so this

is the correct link but if you see chain

excl org that's fine as well and you

should scroll down to the recommended

test Nets section to make sure you're on

the most up-to-date test net at the time

of recording like I said we're working

with sepolia throughout this course we

are going to show you how to work with

different test Nets and different

networks as well because because it's

incredibly important to do so the

blockchain world is moving into a

multi-chain world and especially with

the popularity of l2s which help

ethereum scale learning the differences

between different chains and different

l2s is incredibly important now same as

ethereum what we can do is we can

actually go to sepolia etherscan so

we'll go to sepolia etherscan.io and we

can grab our address from metamask by

clicking and copying the address here

pasting it into the sapoia Explorer and

same as ethereum we can see our account

balance we have zero eth there are no

transactions no token transfers nothing

because obviously it's a brand new

wallet now I'm showing you this because

pretty soon we're going to send our

first ever blockchain transaction if

you've never sent a blockchain

transaction before we're going to do it

on this test net to give you some

confidence as what a transaction

actually looks like when you do move

over to a main net and I'm showing you

this site now because you're going to

see when we send a transaction a lot of

this information is going to get updated

now just remember like I said earlier a

test net is run out of the goodness of

people's hearts so please use the

transactions sparingly once you send

your first transaction here try not to

send too many more as one as good enough

for you to see what's going on anyways

and in order for us to simulate one of

these transactions we're going to go to

a faucet for a testnet testnets have

this thing called faucets which allow us

to get some free sapoia eth so that we

can test out sending transactions and

receiving transactions if you go to the

GitHub associated with this course or

web3 dev.

education we can scroll down to this

testet faucets section and select one of

the links to go to one of these test net

faucets right now the recommended faucet

that we're working with is faucets.

chain. link But be sure to use the

GitHub repo or web 3d. education to be

most up toate what this is going to do

is we're going to ask this faucet site

to send us testnet ethereum and this is

why this test net ethereum isn't worth

any real money since we can get it for

free anytime that we want these

obviously don't exist on mainnet you

can't get free mainnet ethereum via a

faucet now what we can do is we can

actually connect our wallet to this site

and we can get some free test net sapoia

eth this will make it so that in our

balance here we'll actually have some

seoa eth to play with so to do this what

we're going to do is we're going to go

ahead and hit connect wallet accept the

chain link terms of service I've already

read them our metamask is going to pop

up to connect it to this website now get

familiar with this interface because

this is how websites will interact with

our wallet and interact with the

blockchain connecting our account to the

site will first select the specific

account that we want to connect we're

just going to choose account one we'll

hit next and then we'll go ahead and hit

connect and now we can see our wallet

address in the top right and we can see

that we're connected on the ethereum

supp a test net if we go up to our

wallet and we actually switch to

ethereum mainnet you can see that the

website has actually changed this little

drop down to ethereum name net and if we

go in here we can actually switch to

ethereum sapoia and our metamask will

pop up with this switch Network button

which will help us switch the network

for us so now we're back on sapoia test

Network connecting to these websites is

how we give these websites a way to

interact and connect with our wallets we

can go and select this hit these three

dots and hit disconnect this account but

don't worry anytime we want to send a

transaction the website has to ask us if

we want to send a transaction so just by

connecting to the site it won't actually

send a bunch of transactions for us and

if we scroll down we can see our wallet

address is placed right here and we can

see we can request test link and we can

also request test eth for now we don't

need any test link so we're going to

leave that off but in the future we will

come back to the site to get some test

link for now we're just going to get 0.1

test ethereum and if all goes well we

should hopefully see it in our sapoia e

here in order for us to get this test

ethereum we do have to log in Via

Twitter if you don't have a Twitter you

can use any of the other facets in the

test Nets facets area of the GitHub such

as the Alchemy seoa faucet or the sapoia

proof of work faucet but if you are on

Twitter now is a great time to give me a

follow maybe give me a shout out and

maybe say hey sending my first

transaction

thanks Patrick Alpha C or not whatever

you want to do just some light Shilling

of my own Twitter account anyways we can

log on Via Twitter we can authorize this

app verify that we're human give our AI

overlords The Prompt here oh make sure

we don't select the link and let's go

ahead and send the request now what's

going to happen is it's going to give us

this transaction hash on sapoia and

after a delay we'll see it go from

initiating to waiting for confirmation

to token transferred and we'll see a

transaction hash and if we click the

transaction hash we'll see a transaction

that was sent to our address so this

will be the first transaction that we

get to see and there's a ton of

information here but the most important

piece is if we open up our metamask now

we can see we now have 0.1 spolia eth in

our account and if we copy the address

again we paste it into here we can see

now we have a 0.1 eth balance

you might have to wait several minutes

for the transaction to finish going

through and if you accidentally refresh

your browser again we can go ahead and

just select our metamask copy our

address and paste it into ether scan or

just view it right in our metamask here

and if you missed that piece about the

transaction data if we go back to ethers

scan with our address remember we're on

sepolia ether scan and we scroll down we

can see this most recent transaction

hash that just occurred and we can click

the link here and we can see that detail

about the transaction again here now

importantly remember though this is on

sapoia if we switch back to mainnet

ethereum you'll see we have zero eth on

mainnet ethereum if we switch to gly

test Network you'll see we have zero gly

eth on that network if we switch to

Linea gelli eth or any other network

other than sapoia you'll see that seoa

is the only one that has the 0.1 sapoia

eth if you want to practice working with

a different test net feel free to scroll

up back to the faucet select a different

test net and try to get test net in one

of these different test Nets just be

sure to take a look at what test Nets

your metamask comes with since some of

the networks this faucet is compatible

with don't come built into our metamask

but again like I said in the future I'll

teach you how to add these different

networks to our metamask in the future

but huge congratulations you received

your first transaction because again

this faucet is US asking them to send us

money it's not us sending money it's

them sending money to us and if this is

the first transaction that you've ever

sent you should be proud of yourself

already give yourself a big Pat in the

back and here's a picture of me holding

a cat with that cat's face all over my

pajamas as of congratulations now once

more let's grab our address paste it

into ether scan here and scroll down and

we're going to learn a little bit more

about what actually went down what

actually happened in this transaction

you can see on ether scan it gives us

some basic detail details it says from

and to from is going to be another

address a different address an address

controlled by the foset and two is

obviously going to be our address and if

we select this transaction hash we can

see even more details in here

understanding all these different fields

is essential to becoming a smart

contract developer and even just a web3

or ethereum or blockchain user so let's

learn a bit of the basics of what's

actually going down in this transaction

the first field on this page is the

trans action hash you can even see a

little question mark here which tells

you a little bit more about it it's a

unique identifier for this specific

transaction on this network so this

specific transaction hash we can even

copy and paste this into the address bar

and we'll get the exact same transaction

back this is the only transaction in the

entire blockchain that will have this

transaction hash it's the unique

identifier it identifies the transaction

of sending 0.1 eth from the faucet

address add to our address we can see

the status of this was successful we can

see the block number and the number of

block confirmations which we will

explain in the future we can see the

time stamp which of course is when this

transaction occurred we can see the from

and to who initialized the transaction

and who it was sent to if we select this

from and open this in a new tab we can

see some details about who actually sent

us this test eth and if we go back to

the transaction detail and keep going we

can see the value here which again if we

roll over it's the value of ether or

testnet ether and then in parentheses

the Fiat value or the dollar value which

of course since this is a test net it's

always going to be zero the value of

this transaction was 0.1

e now what's underneath this value thing

this transaction fee and this gas price

thing what are these if we zoom in a lot

more to these pieces here and we roll

over transaction fee we can see it says

it's the amount paid to the block

producer for processing the transaction

and then gas price is going to be the

cost per unit of gas specified for the

transaction in ether or guay the higher

the gas price the higher the chance of

getting included in a block I'm going to

explain that in a little bit but if we

scroll down even more let's Zoom back

out and we click click to show more we

can see even more details about this

transaction for now we're just going to

click to show less and just focus on the

details that are here so let's talk

about just the concept of transaction

fees and gas for a second because they

are important concepts for you to

understand remember how I said that

these blockchains are actually run by a

group of different nodes well the

question is what's their economic

incentive to keep running these

blockchains are they running them out of

the goodness of their heart well on a

real Network these nodes actually get

paid a little bit of ether for

processing transactions whenever you

send a transaction there is a node

sometimes referred to as a minor or a

validator depending on the network

you're on who gets paid a little bit of

the Native currency of the blockchain to

process that transaction for ethereum

they obviously get paid in ethereum or

for test ethereum they get paid in test

ethereum which again the test ethereum

is worth nothing which is why I said

they're running them out of the goodness

of their heart if you're sending a

transaction on the polygon Network

they're going to get paid in madic the

native token of polygon if you send a

transaction on an L2 like arbitrum or

optimism you're going to get paid an eth

which is the native token of those l2s

this payment is obviously to incentivize

people to continue to run nodes and they

get paid more the more gas you use so

what is gas gas is a unit of

computational measurement the more

complex your transaction is the more gas

you have to pay for example if we hit

more details just really quickly and I

zoom in a little bit more we can see

this section here gas limit and usage by

transaction this means that when we sent

this transaction we limited it to a

maximum of 60,000 gas but in total we

only used 21,000 gas this 21,000 gas

represents how complex this transaction

was it was 21,000 gas units worth of

complexity now for simple things like

sending ether the units of gas are

usually pretty small for example 21,000

units of gas is actually a really small

amount of gas being sent but maybe for

more complex transactions like minting

an nft depositing some funds into a D5

protocol or deploying a smart contract

those are typically going to be more

expensive transactions because they're

more complicated they have to do more

stuff in the future we'll introduce you

to this concept of evm codes or op codes

and if you break down a transaction to

the lowest level this assembly op code

stuff you can actually see exactly how

much each op code costs in terms of gas

don't worry about this at all right now

just know that these transactions are

broken down into many many many many

very very small instructions and each

instruction has a specific amount of gas

the more instructions usually means more

gas like I said we'll explain this much

later in the course don't worry about

this too much here but just know that we

use 21,000 gas now if you take this gas

used and multiply it by the gas price in

eth instead of guay so we'll take 21,000

and multiply it by this gas price in eth

not in guay and hit enter we'll see the

total trans transaction fee of the

transaction and you can see that this

number does indeed match the transaction

fee for you to understand how much eth

you're going to pay for your transaction

you multiply the gas price times the gas

used transaction fee equals gas price

times gas used so this means that

whoever sent us this 0.1 e also paid

0.525 blah blah blah

eth to a blockchain node to a validator

on the sapoia ethereum test net now each

blockchain has their own unique way of

calculating how much transaction fee

someone's actually going to pay for most

evm chains this is the simple algorithm

it's going to be gas used times gas

price after we understand how the

blockchain works more in depth I'll

explain to you what the rest of these

values stand for for now just know that

anytime you make a transaction on chain

you have to pay the validators or the

blockchain nodes a little bit of gas or

a little bit of the Native token of the

blockchain which in our case is eth so

you have to pay a little bit of eth to

the blockchain nodes providing or

sending the transaction sometimes I'll

refer to this just as transaction gas

let's look at an example of this

ourselves if we pull up our metamask we

go ahead and hit expand view as we know

we have two different accounts in here

we have account one and account two

count 1 has 0.1 spolia eth Count 2 has

zolia eth if I send

0.05 from account one to account two how

much do you think I'll have left in

account one let's go ahead and do this

and this is going to be the first

transaction that you send on the

blockchain which is incredibly exciting

as well let's go ahead and hit this send

button in our metamask we'll hit send

we'll hit transfer between my accounts

we'll select account two and we'll say

0.05 suppo eth so we started with 0.1

aoia eth and we're going to send 0.05 to

account two we'll scroll down we'll hit

next we can see some information here

about what's actually going on we can

see some gas information which metamask

automatically prompted for us and it

even gives us the total amount that

we're going to be paying in eth it's

adding this 0.05 eth to the estimated

amount of gas that we actually have to

spend so that at the bottom it says the

amount plus the gas fee is the two of

those combined

the value that we're sending plus the

gas fee and additionally in metamask if

you select this here you can get some

more information about editing our gas

fees the amount of gas that you choose

to spend can be different depending on

how many people are making transactions

with the blockchain the more people are

sending transactions at the same time

the more expensive gas costs are going

to be so if a lot of other people are

also sending transactions right now the

gas price is going to be higher if a lot

of people are sending transactions that

means there's not going to be enough

space for everyone's transaction to get

through so in order to throttle that

they increase the gas price that's a bit

of an oversimplification of what's

happening but if you take that

understanding that'll pretty much work

if you want to specify exactly how much

gas you want to spend you can clict the

advanced tab if you select zero gas

there's a high likelihood that your

transaction will never go through so

we're just going to go with the default

which is usually a good idea so let's go

ahead and confirm we now see a send

transaction in our Q in the activity tab

of our metamask which shows us that we

have a transaction currently sending and

if we click on it and click view on

block Explorer it'll actually open us up

on ether scan and we'll see well mine

was a little bit quick but normally

we'll see a little indexing Tab and we

won't see this having gone through we'll

see it as like indexing or sending or

something like that but after a little

bit it'll actually finish sending you

might have to wait a minute or so for

this to actually finish going through

but it looks like mine was really quick

and same as our last transaction this

has a lot of the same information and if

we scroll down we'll see that of course

we send a different amount of eth

0.05 and we have a different transaction

fee now if we pull up our metamask what

do you think that we're going to see

we're going to go ahead and click expand

view again and we see account one says

0.05 and account two also says 0.05 hm

that's kind of odd I thought we spent

some gas well if we click on the big

accounts button we see exactly how much

eth is in each account you can see we

have

0.499 in account one and 0.05 in account

2 and we can see in our activity history

our account one recently sent 0.05 eth

and account two recently received 0.05

saoa eth now here's the best part of all

this even if you don't want to become a

developer you just learned the basics of

sending a transaction and interacting

with sites using your metamask

congratulations now here's here

something that's incredibly exciting

with just this little bit of information

you now know how to interact with

blockchains and interact with the

ethereum protocol so if you don't want

to learn how to code anything you can go

and you can start interacting with

ethereum and interacting with protocols

with just this much information however

I know most of you guys are here to

learn how to code so let's look under

the hood of ethereum and what is

actually going on with these

transactions and with these gas and with

these blockchains and what's really

going on let's learn all the

fundamentals of a blockchain now if you

want to just go ahead and jump into the

coding go ahead and grab a timestamp

from the description however learning

exactly how the blockchain works is

going to make you an incredibly powerful

developer so let's take a look at that

first so we're going to be going through

this blockchain demo on this site right

here now the creator of the site has a

fantastic video and a fantastic walkthr

blockchain 101 it is right on their site

so if you're looking for another

explanation definitely check out his

video it is absolutely fantastic but the

first thing that we really need to do in

order to understand blockchain in order

to really anything and everything that's

going on here we first really need to

understand this shot 256 hash or hashing

just kind of in general let's first

understand what a hash is a hash is a

unique fixed length string meant to

identify any piece of data they are

created by putting some piece of data

into a hash function in this example the

hashing algorithm used is Shaw 256 now

ethereum actually uses uh this uh this

right here for its hashing algorithm

which isn't quite um Shaw 256 but is in

kind of this sha family but it's it's

really just another way to Hash things

and uh the specific hash algorithm

doesn't matter uh so much so uh this

example uses Shaw 256 but you can

imagine it's the same as the ethereum

hash they're just going to you know

result in a different hash so what's

going to happen in this application here

is whatever data or whatever information

we put into this data section here as

you can see below

this hash changes so what's happening is

this data is running through this Shaw

256 hash algorithm and it's outputting

this unique hash so this hash is a

unique fixed length string that's going

to identify like a blank data piece here

right so if I put in you know my name

like you know Patrick Collins this is

the hash that's going to represent

Patrick Hollins right and you can see

even when I put you know tons and tons

of data in here the length of the string

doesn't change right so it's always

going to be the same amount we can put

almost any amount of data in here there

is an upper limit on the max size of the

data but for all intents purposes we can

pretty much put any length in here and

you'll see too that you know every time

I type in Patrick Collins this hash is

always going to be this 7 e5b right I'm

going to delete it I'm going to do

Patrick Collins again you 7 e5b it's

it's always this this unique hash is

always going to be unique right it's

always going to be this fixed length

string here so now we can take this idea

right of putting this data in here and

we can move on to uh this concept of a

block so with this block concept we're

going to take the exact same thing with

this hash this this data section right

but instead of having everything just

being in this this singular data area

right here we're going to split this

data up into block nuns and data so all

so what we're going to do is we're

actually going to Hash all three of

these to get to get this hash right

we're going to put all three of these

we're going to say all three of these

are combined uh together we're going to

put every all three of them into this

hashing algorithm uh to figure it out so

if I type a bunch of stuff here we can

see that block one with nuns you know

this nuns and this data we're going to

get this hash and as you can see

actually the screen turns red this block

turned red now what happens when I hit

this mind

button when I hit this mind button it's

actually G to take some time it's going

to think for a little bit and we can see

that the nuns here actually changed

right the nuns is different from what it

was before and this hash now starts with

four zeros okay and then it the back

turned green when we're talking about

mining we're talking about minors

solving some type of very difficult

problem that takes a lot of time to do

now in this example here the problem

that the miners had to solve was they

had to find a nuns or or a value in this

nuns section section that when hashed

with at block number one with this data

it would start with four zeros so the

problem here the minor had to solve was

to start with four zeros and the only

way for them to really do that is kind

of this Brute Force you know trying

stuff so they tried one okay one didn't

work okay two nope two didn't work three

no four five six okay five well that

started with one zero but that's not

four and they have to keep trying all

these numbers until they uh get to this

one where you know let's hit mine again

where it has four zeros at the top at

the start now this specific problem

changes blockchain to blockchain right

ethereum has a different problem for

miners to solve um Bitcoin has different

problems for minor solv but this concept

is going to be the same and since

etherium is proof of stake now nodes

actually take turns solving these

problems again we're not going to go too

deep into that right now though so they

have to take um one block is going to be

this this uh this concept is going to be

all this data it's going to be the block

number and it's going to be this nuns

right and so this nuns is the solution

um is is going to be the the number that

they use to get like the solution to the

problem right so if I go to one here you

know and I do this

again we going to hit mine and the nuns

has changed right it went from one to

33,100 and so that's what's happening

when uh blockchain minor ERS are mining

they're going through this process this

very computationally intensive process

of trying to find a nun that fulfills

whatever the problem is so that's really

it actually so that's a block and and

that's really what's happening when

miners are mining they're just looking

there's trial and error Brute Force

trying to find this nut so so now that

we know what a block is let's go to the

next step and figure out okay well

what's a blockchain so here we have an

example of what a blockchain is going to

look like right we have a combination

you know we have back here in the block

section we have one what one block looks

like now here we have multiple different

blocks right each one of these

represents a different block but we have

an additional column here or we have

additional uh variable here so like

before you know we have block nuns and

data right we have block nuns data but

we also have this thing called previous

right and so this is actually going to

be pointing to the previous hash of the

last block so for example if we go to

the the last block in this blockchain it

says previous is 00 ae8 and if we look

at the hash of block number four it's

000000 ae8 and then we look at its

previous it's 4 Z's B9 we have 4 zos B9

and so on all the way back to our first

block which has previous of just all

zeros right and so the block with the

previous of all zeros is going to be

known as The Genesis block so you've

probably heard that before the Genesis

Block it's the first block in the

blockchain where the previous hash

points to a hash that uh doesn't

actually exist now as you can imagine

kind of the same as how this block

worked how the block nuts and data all

go through the hashing algorithm in the

blockchain the block nuns data and

previous hash all go through this

hashing algorithm to figure out you know

what the hash is okay so if we go to

over here you know for example if I type

in you know Patrick obviously this is

now no longer valid right because this

nuns uh combined with the block the data

and the previous hash aren't going to

solve you know our problem of having 4

at the at the start right so I'm going

to go and fix that and and that's that's

kind of an easy way to to see it being

broken but but let's take a look if I

break this block right here what happens

if I if I break the data in here if I do

like Patrick in here you can see that

both of these are now read both of these

are now invalid right because the block

hash with the nuns hash with the new

data which is my name Patrick hashed

withe hashed with the previous block is

now a brand new

right and this block is still pointing

to this previous hash right here right

is pointing to this previous block and

now it is wrong and it is messed up and

now um and now its Nuns with this

previous hash is also wrong right and

this is where when we talk about uh

blockchains being immutable this is

exactly how it's immutable right because

I go back and I change anything you know

if I just typed a right here the entire

blockchain is now invalidated because

none of these are going to have uh Nunes

that solve this equation anymore so this

is why blockchains are immutable is

because anytime you change one thing you

ruin the rest of the blockchain okay so

however though you know if if an a was

here originally we can go ahead and mine

these we can mine all these but as you

can see you know this is going to start

getting very uh computationally

expensive because I have to go redo uh

basically the entire blockchain uh and

the farther and farther down the line

you get the harder and harder it becomes

to you know rehash and and redo all

these different blockchains here now

this makes a lot of sense right so we

have this blockchain it's really hard to

change something in the past but if we

do we can just go ahead and remine it

now if I'm the one who controls the

blockchain right if I'm the one who

controls this you know and I want to

change something in the past well okay

great all I got to do is change this

data here and then you know mine each

one of these you know obviously it's

going to be very computationally

expensive but it's something that I can

do right if I'm the one who owns the

blockchain now here's where the

decentralized nature or the distributed

nature really uh makes it incredibly

powerful so we're going to go to the

distributed tab here which I also refer

to as the decentralized tab here and

it's going to show us what a blockchain

looks like uh in a decentralized manner

so we have this exact same uh initial

setup here we have distributed

blockchain we have you know the our

first blockchain which is kind of

exactly as the one from here but we also

have more than one so we have Pier a

pier B and Pier C and when people are

talking about Pier to to peer

peer-to-peer transactions they're really

talking uh this is kind of that concept

that they're talking about right so we

have a number of different peers who

running this blockchain technology

they're all weighted equally right each

one of these tiers or each one of these

nodes each one of these entities running

a

blockchain has the exact same power as

anybody else right so the way that we

can tell very easily which blockchain is

correct or which ones are correct are by

looking at this end hash here right by

looking at where we are uh in the

blockchain because again remember

because again remember this this hash

that this this in this last block here

is going to Encompass all of the blocks

from before right because this last hash

is going to have the previous hash here

which includes the previous hash here

which this hash includes the previous

hash here and which so this last hash is

encompasses everything in here right and

we can look we can look at the hash of

Pier C which is four zeros and then E4 B

we can look at the latest hash of Pier B

which is 4's e4b and then Pier a which

is 4 e4b so all of these peers all of

these nodes all of these decentralized

you know these independent um all these

independent users running this

blockchain software they're all matched

up it's very easy for their nodes to

look at each other and say hey great we

are all matched up now what let's say

that a decides that you know something

happened on the blockchain that they

didn't like and they wanted to go back

and change something right so let's say

they change here you know obviously uh

the rest of their blockchain is

invalidated and they have to spend a lot

of computational power to catch up to

speed so let's go ahead and humor it

let's say that they they did they ended

up catching up uh they ended up catching

up you know they ended up mining

everything and now they have a valid

blockchain right it solves the equation

awesome however in block number three

there's something new right this is here

and it shouldn't have been here this is

something that perer a put in by

themselves all that happens now is we

look at all the blockchains that are

running the software and we're looking

at all the hashes at hash at block

number five so per a has this new hash

now

9bc but Pier B has a different hash 00

e4b right so who's right is it is it

Pier a with their new stuff or is it

Pier B well that's where the

decentralized comes in because then we

can look at Pier C and Pier C also has

e4b so Pier B and Pier C both say hey

Pier a you're wrong get out right and P

A will stop being able to participate in

the mining rewards because they have

essentially forked uh the blockchain and

started their own little blockchain

right with their own history because

they're the only ones with this this

piece of data in block three whereas

Pier B and Pier C have nothing in there

so that really shows why uh in these

blockchain worlds in this decentralized

world there really is no centralized

entity you know per a you know might

have been maliciously motivated to

change you know this this block number

three however democracy rules right the

majority rules in the blockchain pier B

and Pier C both say Hey you know that

that's cute and all p a but you're wrong

right that that's not right now it might

be a little abstract that you just look

at data and you know us typing kind of

random stuff in here and think okay yeah

that's that's data right that makes

sense you know just kind of random

strings in here doesn't really do

anything for us so if we actually go

over to the Token section here this is

where everything really starts to make a

lot of sense so we have the exact same

setup here uh with Pier a pier B Pier C

except the difference is instead of

having kind of this this data section we

have this a TX this transaction section

right and this represents all the

transactions that are happening in this

block right so we're we're sending $25

from Darcy to Bingle or to Bingley uh

for uh $27 here 1922 right and it's the

exact same thing so this all these

transactions are going to get hashed in

the exact same way uh that the data is

going to get hashed and and this is why

it's so powerful because again you know

if I want to be malicious right if uh if

I wanted to say hey I I really wanted to

give Jane a lot more money from

Elizabeth so I'm p and I go back and I

change it to 100 well now you know not

only do I does my whole blockchain uh

get invalided because that was so far uh

so long ago but I'm not going to match

any of these other chains right and so

my blockchain is going to be excluded

from the overall blockchain so and let's

let's go ahead and fix this and it's the

same thing if down here if I I become

malicious and I want to send you know I

want uh Miss Audrey to have less money

maybe I want to send a dollar and I go

ahead and M it the same thing here this

hash now this 2a1 is not going to match

pib's pb's hash of BBA and it's not

going to match PC's hash of BBA as well

so the two of them are going to say hey

this your blockchain is invalid it's not

matching the majority you know you're

out right so that's really how uh these

blockchains work at a low level and it

all goes back to this this understanding

this hash idea and using it in this very

sophisticated manner uh to kind of

cryptographically prove um you know

where where stuff lies now the way the

blockchain works is you instead of

random stuff put in this data section

it's actually going to be solidity code

in here to finding ways to interact with

different blocks and different protocols

that are on chain or as we've said

before different smart

contracts now the next question that you

might be asking is okay well how do I

know how can I be sure that I'm the one

uh you know let's say this is let's say

I'm Darcy right how can I be sure that I

was that Darcy was the one to actually

send this money here how do we know that

Darcy sent $25 to uh Bing

well this is where we get into private

keys and public keys and that's what

we're going to go into now let's just do

a quick recap of what we've learned in

this section so far right we've learned

that ethereum actually runs on this Kack

256 but you know we used shot6 for this

demo it doesn't really matter we're just

talking about hashing algorithms so

again a hash is a unique fixed length

string meant to identify any piece of

data a hash algorithm or a hash function

is a function or algorithm that computes

any type of data into a unique hash

mining is going to be the process of

finding the solution to the blockchain

problem in our example the problem was

finding a hash that starts with four

zeros nodes get paid for mining

different blocks and the problem is

going to be different blockchain to

blockchain a block in a blockchain is

basically a combination of a block nuns

transaction and a previous hash to

create this unique hash for this block

and again depending on the blockchain

implementation this might have a couple

other fields or might have different

fields but this is essentially what's

going on blockchains are decentralized

and distributed because many independent

users are going to run this blockchain

software and they will check and they

will compare against each other to see

which blockchains are acting honestly

and which ones are acting maliciously in

the blockchain world majority rules the

nuns here is the answer used or the

number used to get this hash now nuns is

kind of an overloaded term it's actually

used for a number of different reasons

in this case we're using it to solve

this problem of getting you know four or

five zeros at the stop of the hash

however in ethereum it'll also be often

used as the number of transactions from

a given

address so now we're going to talk a

little bit about signing these

transactions and and private keys and

and some other cryptography pieces right

because in this blockchain demo here we

can see we have all these these

fantastic transactions right all these

things went through but how do we know

that it was dar see who is the one to

send $25 uh to Bingley right how do we

know that actually happened and this is

where all those pieces that we just

learned about uh in our our test net in

our metamask account are really going to

start to to come to life here a little

bit here so here we have an example of

public and private Keys okay at the top

we have this private key right that was

that was randomly generated uh a private

key is is you know as it kind of states

is a key that you really want to keep

secret because you're going to be using

this uh as kind of your your secret

password for all your transactions right

I can really pick you know any any any

private key anything that I want and

with it uh this algorithm they're going

to use an algorithm you know for

ethereum and Bitcoin they both use this

elliptic curve digital signature uh

algorithm it's it's a variant of just a

digital signature algorithm and it's

going to create this this public key

right I'm really not going to go at all

into kind of this digital signature

algorithm but just know it does use some

of these uh some of the hash uh

knowledge that we just learned combined

with some other pieces uh to kind of get

this this public here so I'm not going

to go too deep into it but we have this

private key that we create and we get

this public key now this public key we

want everybody to have access to right

this is yeah whole world can see this

this private key we really want it to be

uh private we don't want people to see

this we're going to use this private key

as like a password to quote unquote

digitally sign transactions and then

people can verify them with this public

key so let's let's see what this

actually looks like let's pick a a

random key a more secure key right

because the longer it is the the more

secure it's going to be and if we go to

signatures now right um let's say we

have this uh this message that we want

right we say high world right we want

this to be the message what's going to

happen is this private key that we've

created we can use to sign this data

right remember how in the blockchain

demo you know we were kind of We Were

hashing stuff right we were we're using

this uh shade 256 hash to to get this

hash well we're doing something similar

but instead of hashing we're we're using

this digital signature algorithm to

create this message signature now what's

really powerful about how this uh this

algorithm works is that you can create

this message signature with your private

key but somebody else can't derive your

private key from the message signature

and that's what makes this really really

powerful however if we go to verify by

using this public key right uh and so

this is the this is that 0403 this is

that same public key using this uh using

this public key anybody can verify oh

let's go ahead and sign it again anybody

can verify that this signature is yours

right so you have a public a private key

just for you so you can sign things and

a public key that anybody can verify

something right so anybody can verify

this and let's say somebody tries to

fake a transaction from you they say Hey

you know this is this is this is their

transaction um all they have to do is

verify that this signature against your

uh public key and very easily this whole

thing turns red because uh it isn't

verified right the the algorithm says

Hey uhuh that's wrong so we can go ahead

and take that into transactions in this

exact same way so if I want to send

money you know if I want to send $400

from you know my address to another

address using my private key I can sign

that transaction and anybody else in the

world can then verify this transaction

right and this is why when people say

hide your keys you know protect your

keys this is what we're talking about in

our accounts here right if we go to uh

settings and again the only reason that

I'm showing you guys my pneumonic and my

private key is because this is a uh this

is a dumpster account I'm going to throw

this away at the end of this video or

I'm just not going to put any real money

it um

but when we look at our our our metamask

here we have this numic phrase which

allows us to easily get these different

private keys right so uh pneumonic

phrase combined uh with you know uh

whatever account number will get us a

private key so pneumonic phrase combined

with one we're going to get this private

key and this is when we look at Account

Details export private key

confirm this is going to be the private

key that we're going to use to sign our

transactions right this if anybody else

gets access to this private key they

then can sign transactions for us and

they can send transactions for us and

that's why we want to keep these private

so uh it works the exact same way right

so this is why it's so important to hide

your private keys and hide your newonics

now your ethereum address is actually uh

a piece

uh is actually a piece of your public

key now to get our address in ethereum

all we have to do is take this public

key that we've created with our private

key hash it using that same ethereum

hashing algorithm and then take the last

20 bytes and that's how we'll actually

derive to our um to our address here now

knowing the exact methodology of how to

get the address doesn't really matter

because it could change blockchain to

blockchain and could even change e two

um but just know that that is

essentially how kind of these addresses

are derived right there some derivative

of the public key right because the

public key is public and you know uh

using the public key in kind of any

public way is is totally fine um but not

the private key so that is how we sign

our transactions note though this isn't

how we send the transactions so so this

is just going to sign it create a

transaction for us to send uh we'll

learn later on how to send these

transactions so that was a lot of

information there too let's do a quick

recap your public key is derived by

using a digital signature algorithm on

on your private key right and you want

to keep your private key private at all

times because you're going to use your

private key to sign transactions signing

transactions with your private key you

are the only one who can actually do

this because you can't get the private

key from a message signature however

using your public key you can anybody

can very easily verify that a signature

that's signed by you is in fact signed

by you in our metamask our private keys

are located in this Account Details

section you just hit uh show Private

keys and type in your password and

you'll get your your private key here

and the address of your account is

derived from this private key uh it's

derived from this public key so if you

think about it your private key creates

your public key which then can create

your address and there's a little

barrier

here or a big barrier here because your

private key you want to keep private and

your public key and your address can all

be public information now remember

remember how in our metamask we were

able to actually create new accounts

mine says account six cuz I've created

actually a few but how was it actually

creating those accounts well now that we

know all this if we go back to our

blockchain demo here what our metamask

is doing is essentially taking our

pneumonic or or that multi-word secret

phrase and then just hashing it with

some number so secret phrase plus 0 gets

this and it'll set this as your private

key and for our account one that'll be

the private key or maybe it's plus one

the exact algorithm that it's using

doesn't matter but if you want to create

a new private key where you just hit

this create account button the way it

actually picks this account is by taking

this secret phrase and then just

changing this number so if I go if I'm

in my metamask I do create account this

right now I'm on account six because

like I said I made a whole bunch if I

make account six right it's as if we

just did the secret phrase plus six and

created this new hash or this new

private key and created this new hash

and it uses this to make a private key

and this is why in your metamask if you

share that secret phrase if you share

that pneumonic device they will have

access to all the accounts that you ever

created however if you share your

private key it will just give them

access to that single account secret

phrase has access to all the accounts

created in your metamask or your wallet

your private key is access to that

single account and then the public key

or address anybody can have access to

and it's cool for anybody to have access

to so when I'm thinking about the

security of my metamask or my wallet

this is kind of the order that I think

of it in the seed phrase or pneumonic or

secret phrase is incredibly important

protect this at all costs because if

somebody else gets access to this they

will have access to all of your accounts

the second most important is the private

key because if somebody gets access to

that they will get access to a single

account and then your public key or

address which whatever it's public

now that we know a little bit more about

what's going on underneath the hood of

these blockchains let's go back at our

transactions and look at this gas thing

again and we'll look to see what's

actually happening here gas in

particular can be a little bit tricky to

wrap your head around so if you don't

get it right away don't worry as we go

through examples it'll start to make

more sense so before I was saying let's

just look at this transaction fee bit

which is the cost associated with

running this transaction if I scroll

over this on ether scan I can see this

thing that says Block Base fee per gas

plus Max prity fee per gas times the gas

use which might be a little bit

confusing here let's actually break down

what's going on on ethereum with EIP

1559 in place and again this is going to

be specific to ethereum as every

blockchain might do it a little bit

differently but if we click to see more

we can see a number of useful values

here we can see gas limit is 21,000 and

usage is

21,000 so this transaction used 21,000

gas and we sent 21,000 gas along with it

sometimes when sending a transaction

depending on when it's sent and

depending on what these Specific

Instructions are it might actually use

way more gas than what you want it to

use so with your transactions you can

actually set a limit hey I don't want to

use more than x amount of gas I don't

want to do more than x computational

units and in fact if we go to our

metamask and we click Send to transfer

between accounts again

and we pick you know 0.01 e or something

next can actually hit this little button

here go to Advanced and we can actually

edit some specifics of this transaction

one of them is going to be the gas limit

we can change this gas limit to maybe

2200 2300 or more or even less since

sending ethereum takes exactly 21,000

gas metam Mass just defaults to setting

into that but we also see these other

interesting things we see a priority fee

and a Max base

fee let's reject this transaction and

let's look back at ether scan to talk

about these So currently in ethereum

according to e EIP 1559 every

transaction on ethereum comes with

something called the base fee this is

the minimum gas price you need to set to

include your transaction and you'll

notice that these are priced in

something called guay so what is aay if

we come to the site ethon converter.com

and again there's a link to this in the

GitHub repository we scroll down we can

see whey guay and ether if I put one

ether in here I can see how much one

ether is in terms of guay and in terms

of wayy one ether is equal to one 2 3 4

5 6 7 8 nine nine zeros so that's that's

one billion guay is going to be one

ether and then 1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18

and then 18 zos is away these are just

easier ways of referring to really

really small amounts of ethereum so if

we look at our gas fees we see that the

base fee is

0.00004 gay and this obviously would be

an even smaller number if this was in

units of way so if we take this number

and we put it into our calculator we can

see that this is equal to 40 way or 0.

a whole bunch of zeros for ether the max

fee here refers to the maximum gas fee

that we're willing to pay for this

transaction and you can actually see

that our Max fee is a little bit higher

than what we actually ended up paying

our Max fee was 2.21 32 something

something and the gas price we actually

paid was up here now your transaction

might of course be a little bit

different then additionally we have a

Max priority fee this is going to be the

max gas fee that we're willing to to pay

plus the max tip that we're willing to

give to miners now currently in ethereum

this base fee ends up getting burnt and

we can see on ether scan exactly how

much is getting burnt here and if we

pull up our calculator again we can grab

this gas fee multiply it by the amount

of gas we used and we can see that this

is indeed how much ethereum we actually

ended up burning we go back to ethereum

converter paste it in we can see that

these two numbers are indeed equ

this means whenever you send a

transaction a little bit of ethereum is

removed from circulation forever or it's

considered burnt So currently in

ethereum part of your ethereum part of

your transaction fee actually gets burnt

and then the other part goes directly to

miners so to figure out exactly how much

went to minors we could do this number

minus the burnt amount and this is how

much ethereum was paid to an ethereum

minor for this transaction you'll see

down here transaction type 2 EIP 1559

this is the EIP 1559 version of these

transactions like I said every

blockchain is going to have a different

fee burning and and fee and gas process

and they're all going to be a little bit

different but the sum of it is

blockchains have limited block space for

transactions the gas price that costs

for your transaction to be included in

one of these blocks changes based off

how much demand there is the base gas

fee for ethereum will go up and down

depending depending on how many people

are sending transactions and how many

people want to be included in a block if

a ton of people want to be included in a

block that means a ton of gas is

obviously going to get burnt we've left

a link to a video in the GitHub

repository with this section from this

YouTuber who does an amazing job

breaking down this EIP 1559 and more

about how this gas model actually works

I highly recommend you pause this video

and watch that video to understand more

the base fee gets programmatically

algorithmically adjusted to try to

Target for all the blocks to be 50% full

if they're more than 50% full this base

fee automatically goes up if they're

less than 50% full this base fee goes

down now this is a lot of the basics of

how this transaction works and it can be

a little confusing so let's do a quick

refresher of everything in here there's

a unique transaction hash that uniquely

identifies this transaction on this

blockchain we can see the status we can

see the block number that it's confirmed

on one other thing we want to look at if

we scroll up we see block number and

block confirmations this is how many

blocks have been mined since this block

was included like we saw with our

blockchain demo the longer the

blockchain gets the harder it is to

tamper with and the more secure it is

typically you'll see some processes say

they'll only do something after 20 block

confirmations 30 Block confirmations or

or Etc the reason that they wait for

these block confirmations is because

they want to make sure that that

transaction is actually included and we

can actually see the block that our

transaction was included in and all the

other transactions with it different

details about how much gas was used the

gas limit Etc time stamp is when the

transaction happened we can see from and

to we can see the value and then we can

see the transaction fee which we see

right here is Block Base fee per gas

plus the max priority fee per gas times

the gas used and we see all the details

of the gas down here gas price is the

cost of one unit of gas gas limit is the

max amount of units of gas that we're

willing to pay in this transaction the

usage is how many actually got used the

base fee is going to be the base Network

fee per gas so 40 way per one gas used

the max gas is the max gas price we're

willing to pay and Max priority is going

to be the max gas price plus the tip

that we give to Miners and then we can

see how much is burnt and then we see

transaction savings which which is the

difference between how much was actually

used or paid for and then returned so

for example in this transaction the gas

price we ended up picking was a little

less than our Max gas price here so the

gas price we ended up using was a little

less than our Max priority fee here so

we had some savings compared to that we

can also see that this was an EIP 1559

transaction we can see our nuns here

which was nuns zero because the

transaction that I'm showing is our

first nuns and then of course we can see

the input data for transactions that are

just sending ethereum the input data is

going to be blank but you'll see that

when we get to Smart contracts the input

data is not going to be blank and it's

going to be one of the most important

features of these transactions you'll

also notice that there's a state tab

this is an advanced Tab and it shows the

different states that are changed based

off of this transaction where we're

going to ignore this one for now now

that we know how the blockchain itself

Works under the hood let's talk about

some blockchain fundamentals and we

actually covered all these topics in a

previous free code Camp video so let's

go to

that if the first time you listen to

this some of these Concepts seem a

little bit hard to grasp don't worry

about it as we continue and as we move

on with this course they'll start to

make more sense when you see them used

in real examples I definitely would

recommend going back and rewatching and

Rel listening to the parts that you

don't quite get and asking questions in

the discussions tab of the GitHub

repository awesome so now that we know

all the cryptography pieces and all the

little nitty-gritties of how the

blockchain actually works and how our

signatures work and how everything

sticks together let's talk a little bit

about how this works in actuality and

what's really going on now for a lot of

this each different blockchain has

slightly different algorithms and

slightly different metrics and criteria

for doing a lot of this stuff so when

we're talking about these specific

implementations keep in mind the exact

algorithm might be a little bit

different but the concepts are all still

going to be exactly the same hashing and

hash function is going to be the same no

matter where you look a decentralized

blockchain is going to be the same no

matter where you look how it's actually

implemented is going to be a little bit

different now traditionally when you run

an application you know be it a website

or something that connects to some

server you are interacting with a

centralized entity and unlike how we saw

with the blockchain with multiple

different peers it's going to be run by

a single centralized group now it still

could be run on many different servers

but all those servers are still going to

be controlled by the same centralized

group blockchains as we saw run on a

network of different independent nodes

when we saw Pier a pier B Pier C those

were different examples of different

independent users running the blockchain

technology on their own node now when I

use the term node I'm usually referring

to a single instance of a decentralized

system so when I say a single node when

I'm talking about a blockchain I'm

talking about one of those perer A's

Pier B's perer C's running that

blockchain software I'm talking about

one server running this technology and

again it's this network it's this

combination of these nodes interacting

with each other that creates this entire

blockchain what makes these so potent

too is that anybody can join the network

and that's why there's decentralized the

barrier to entry is a little bit of

Hardware requirements you getting the

correct materials to run the software

and then you running the software

anybody can join these networks and

participate and that's what makes it

truly decentralized in fact you can go

to GitHub right now and run your own

ethereum node in a few seconds now in

the traditional World applications are

run by centralized entities and if that

entity goes down or is maliciously

bribed or decides that they want to shut

off they just can't because they're the

ones that control everything blockchains

by contrast don't have this problem if

one node or one entity that runs several

nodes goes down since there are so many

other independent nodes running that it

doesn't matter the blockchain and the

system will persist so long as there is

at least one node always running and

luckily for us most of the most popular

chains like Bitcoin and ethereum have

thousands and thousands of nodes and as

we showed in our demo if one node acts

maliciously all the other nodes will

ignore that node and kick that out or or

even punish it in some systems because

they can easily check everybody else's

note and see okay this one is out of

sync with the majority and yes majority

rules when it comes to the blockchain

each blockchain keeps a full list of

every transaction and interaction that's

happened on that blockchain and we saw

if a node tries to act maliciously then

all their hashes are going to be way out

of whack and they're not going to match

everybody else this gives blockchains

this incredibly potent immutability

trait where nothing can be changed or

corrupted so in essence we can think of

a blockchain as a decentralized database

and with ethereum it has an extra

additional feature where it also can do

computation in a decentralized manner

now let's talk consensus proof of work

and proof of stake because you've

probably heard these before and they're

really important to how these

blockchains actually work when we went

through that blockchain example and we

did that mining feature this is what's

known as proof of work proof of work and

proof of stake fall under this umbrella

of consensus and consensus is a really

important topic when it comes to

blockchains consensus is defined as the

mechanism used to reach an agreement on

the state or a single value on the

blockchain especially in a decentralized

system I briefly alluded to this

consensus mechanism in our blockchain

example when I said if one changes

something and the other two don't then

majority Will Rule and kick that one out

this is part of that consensus mechanism

now very roughly a consensus protocol in

a blockchain or decentralized system can

be broken down into two pieces a chain

selection algorithm and a civil

resistance mechanism that mining piece

that we were doing or or the proof of

work algorithm is what's known as a syil

resistance mechanism and this is what

ethereum and Bitcoin currently use

please note that depending on when

you're watching this if eth 2 is out

then it's no longer proof of

work now proof of work is known as a

civil resistance mechanism because it

defines a way to figure out who is the

block author which node is going to be

the node who did the work to find that

mine and be the author of that block so

all the other nodes can verify that it's

accurate civil resistance is a

blockchain's ability to defend against

users creating a large number of pseudo

Anonymous identities to gain a

disproportionately advantageous

influence over said system and in

layman's turns it's basically a way for

a blockchain to defend against somebody

making a bunch of fake blockchains so

that they can get more and more rewards

now there are two types of civil

resistance mechanisms that we're going

to talk about here namely proof of work

and proof of stake let's talk about

proof of work work a little bit more in

depth first in proof of work this is Cil

resistant because a single node has to

go through a very computationally

expensive uh process called mining which

we demonstrated earlier to figure out

the answer to the blockchain's riddle of

finding that correct nuns or or whatever

the blockchain system has in place in

proof of work this works because no

matter how many pseudo Anonymous

accounts you make each one still has to

undergo this very computationally

expensive activity of finding the answer

to the proof of work problem or the

proof of work riddle which again in our

demonstration it was finding a Nuns with

that first four zeros but again each

blockchain might change the riddle or or

change the problem to be a little bit

different in fact some of these

blockchains make this riddle

intentionally hard or intentionally easy

to change What's called the block time

the block time is how long it takes

between blocks being published and it's

proportional to how hard these

algorithms are so these problems

actually can change depending on how

long they want the block time to be if a

system wants the block time to be very

very long they just make the problem

very very hard if they want to be very

short they make the problem a lot easier

we'll talk about cibil attacks in a

little bit and how they can affect the

system but with proof of work it's a

verifiable way to figure out who the

block author is and be civil resistant

now you need to combine this with a

chain selection rule create this

consensus now there's some consensus

protocols that have more features but

very very roughly these are the two

pieces that we're going to look at the

second piece is going to be a chain

selection role how do we know which

block chain is actually the real

blockchain and the true blockchain now

on bitcoin and ethereum they both use a

form of consensus called Nakamoto

consensus and this is a combination of

proof of work and longest chain

roll the decentralized network decides

that whichever blockchain has the

longest chain or the most number of

blocks on it is going to be the chain

that they use this makes a lot of sense

because every additional block that a

chain is behind it's going to take more

and more computation for it to come up

that's why when we saw in our

transaction we actually saw

confirmations the number of

confirmations is the number of

additional blocks added on after our

transaction went through in a block so

if we see confirmations as two it means

that the block that our transaction was

in has two blocks ahead of it in the

longest chain now I do want to point out

that a lot of people use proof of work

as a consensus protocol and I do want to

say that this is a little bit inaccurate

but sometimes people use it

interchangeably proof of work is a piece

of the overall consensus protocol which

in Bitcoin and ethereum 1's current case

is Nakamoto consensus nakomo consensus

is a combination of proof of work and

this longest chain rule both equally and

very very important now proof of work

also tells us where these transaction

fees and these block rewards go to

remember how when we made this

transaction we had to talk about gas and

a transaction fee so who's getting paid

who is getting this transaction and this

transaction fee is going to the miners

or the validators in a proof of work

Network they're called Miners And in the

proof of stake Network they're called

validators there are a little bit

different and we'll get into that when

we talk about proof of stake in this

proof of Works system all these nodes

are competing against each other to find

the answer to the blockchain riddle

remember in our example it was to find a

hash that has four zeros at the start

and again depending on the blockchain

implementation that riddle is going to

be a little bit different but all the

nodes are trying as many as possible to

try to get this answer first why because

the first node to figure out the answer

to the blockchain re is going to get

that transaction fee they're going to

get paid from that now when a node gets

paid they actually get paid in two

different ways one is going to be with a

transaction fee and another piece is

going to be the block reward remember

how we talked about alternating the gas

price or the guay on our transaction

well that's the transaction fee that

we're going to pay to these blockchain

nodes for including our transaction the

block reward is given to these nodes

from the protocol from the blockchain

itself you've probably heard of the

Bitcoin having before the having is

referring to this block reward getting

cut in half and it's supposed to be cut

in half roughly every four years this

block reward increases the circulating

amount of whatever cryptocurrency that

is being rewarded for example on

ethereum the Block reward is giving out

ethereum and on bitcoin the block reward

is giving out Bitcoin so these nodes are

competing against each other to be the

first one to find this transaction to be

the first one to find the answer to this

problem so that they can be the ones to

win both this block reward and your

transaction fee some blockchains like

Bitcoin for example have a set time when

they're no longer going to give out

block rewards and the miners or the

nodes are only going to get paid from

transaction fees now this gas fee again

is paid by whoever initialized the

transaction when we got our funds from

the faucet there was some server and

somebody else was paying the transaction

fee for us however when we sent ether

from one account to another our first

account actually paid some transaction

fee to send that ether in proof of stake

there's also a gas fee but it's paid out

to validators instead of Miners and

we'll talk about that in a little bit

now let's talk about two types of

attacks that can happen in these

blockchain worlds let's talk about the

first one being the cibil attack the

cibil attack is when a user creates a

whole bunch of pseudo Anonymous accounts

to try to influence a network now

obviously on bitcoin and ethereum this

is really really difficult because the

user needs to do all this work in proof

of work or have a ton of collateral in

proof of stake which again we'll talk

about in a bit the other more prevalent

attack is what's known as a 51% attack

now as we saw as part of our consensus

protocol these blockchains are going to

agree that the longest chain is the one

that they're going to go with so long as

it matches up with 51% of the rest of

the network this means that if you have

the longest chain and you have more than

51% of the rest of the network you can

do what's called a fork in the network

and bring the network onto your now

longest chain now Cil attacks obviously

are when a single node or a single

entity tries to affect the decentral of

the network by pretending to be multiple

different people although they're just

the same person or entity and like I

said it's really difficult to do in

proof of work and proof of stake so you

can see now that blockchains are very

Democratic whichever blockchain has the

most Buy in and is the longest is the

blockchain that the whole system is

going to corroborate when nodes produce

a new block and add it to the longest

chain the other nodes will follow this

longest chain that the rest of the

network is agreeing with ADD those

blocks to their chain and follow up so

very small reorganizations are actually

pretty common when a blockchain picks a

block from a different longest chain

puts it on and then has to swap it out

for another block and continue with a

different blockchain however if a group

of nodes had enough nodes or enough

power they could essentially be 51% of

the network and influence the network in

whatever direction that they wanted this

is what's known as a 51% attack and it's

happened on blockchains like like

ethereum classic which is not ethereum

this is why the bigger a blockchain is

the more decentralized and the more

secure it becomes so after you watch

this video and you become a blockchain

engineering expert I definitely

recommend you run a note as well because

you are going to increase the security

of the network as a whole by running a

node so proof of work is fantastic

because it allows us to very easily

protect against these Cil attacks and

keep our blockchains decentralized and

secure however it has some drawbacks as

well proof of work costs a lot of

electric

because every single node is running as

fast as they can to win this race to get

the rewards this leads to obviously an

environmental impact now since proof of

work in Nakamoto consensus a lot of

other protocols have taken this idea and

gone in a different direction with a

different civil resistance protocol a

lot of them with the intention to be a

lot more environmentally friendly and

the most popular one right now is proof

of stake there are some chains that are

already using this proof of stake

protocol and that are live and thriving

some of them are like Avalanche Sal

polygon polka

dot so let's talk about proof of stake

now again this is a different civil

resistance mechanism instead of solving

this difficult problem proof of stake

nodes put up some collateral that

they're going to behave honestly AKA

they stake in the example of ethereum 2

nodes put up some ethereum as a stake

that they're going to behave honestly in

the network if they misbehaved in the

network they are going to be slashed or

removed some of their stake obviously

this is a very good civil resistance

mechanism because if you try to create a

whole bunch of anonymous accounts then

each one of those accounts you have to

put up some stake and if you misbehave

you're going to run the risk of losing

all the money that you put up as

collateral in this system miners are

actually called validators because

they're no longer binding anything

they're actually just validating other

nodes now unlike proof of work which

every node is racing to be the first one

to find the Block in proof of stake

nodes are actually randomly chosen to

propose the new block and then the rest

of the validators will validate if that

note has proposed the block honestly as

we saw with our cryptography lesson it's

usually very easy for other notes to

verify if a proposal or a transaction is

honest now proof of stake obviously has

some pros and cons as well Pros are that

again it is a great civil resistance

mechanism and a great way to figure out

who the author of a block should be the

other Pros are that it's way less

computationally expensive to figure out

the new block because instead of every

single note on the network trying to do

this only one node needs to do this and

then the rest of the nodes just need to

validate it the cons are that it's

usually considered a slightly less

decentralized Network due to The Upfront

staking costs it costs to participate

now this gets into a little bit of a

philosophical battle on how

decentralized is decentralized enough

and I think that's up to the community

to decide and as we progress I think

we'll learn more and more about how

decentralized is decentralized enough

the general consensus amongst blockchain

Engineers though is that proof of stake

is very very decentralized and very

secure now there's another term that

might be the first time you heard it a

layer one we're going to talk about

layer ones and layer twos in terms of

scalability really quickly as well a

layer one refers to any base layer

blockchain implementation bitcoin's a

layer one ethereum's a layer one

Avalanche is a layer one these are the

base layer blockchain Solutions a layer

two is any application that is added on

top of a layer one added on top of a

blockchain some examples of layer twos

are going to be chain link arbitrum or

optimism arbitrum and optimism are very

interesting because they are layer twos

that also look to solve this scalability

issue arbitrum and optimism are what's

known as rollups and they roll up their

transactions into a layer one like

ethereum we're not going to go too deep

into rollups and how they actually work

but all you really need to know is that

they solve some of the scalability

issues by being another blockchain that

people can make transactions on still on

kind of this base ethereum layer now

they're different from side chains

because side chains derive their

security from their own protocols

rollups derive their security from the

base layers so arbitrum and optimism for

example is going to be just about as

secure as ethereum there's some

fantastic guys in there that go a little

bit deeper into rollups and I've left a

link in the description for you all

right so we just talked about a lot of

stuff so let's do a quick recap before

moving on civil attacks are prevented

due to protocols like proof of work and

proof of stake 51% attacks grow

increasingly harder with the size of

blockchain so you should run a node

consensus is the mechanism that allows a

blockchain to agree upon what the state

of the blockchain is sharding and

rollups are solutions to scalability

issues on layer ones a layer one is any

base blockchain implementation like

Bitcoin or ethereum a blockchain

scalability problem is that there's not

always enough block space for the amount

of transactions that want to get in them

this leads to very high gas prices and

again gas prices are how much it costs

to interact with a blockchain

so that's it for the blockchain basics

and the blockchain explainers with just

this information you now can go off into

the world and start working with

blockchains and interacting with

blockchains with at least some level of

knowledge as to what's going on you

should be incredibly proud of yourself

for just making it this far definitely

be sure to give yourself a pat on the

back and Round of Applause now that

we've gotten a lot of the basics and the

fundamentals out of the way let's start

jumping into the coding aspect this is

where you're going to learn how to

actually build these smart contracts how

to build these trust minimized

agreements in these blockchains and in

these smart contract platforms this next

section this solidity Basics the

solidity fundamentals section will give

you all the skills to start actually

coding solidity and understanding how

these smart contracts work underneath

the hood so at this point absolutely

give yourself a high five maybe say hi

in the GitHub discussions maybe say hi

high in the community on Twitter on

Reddit Etc and be proud of just making

it this far the journey has really only

just begun but you've already learned so

much let's begin the next section and

let's jump into the

code now that we're going to to the

coding part I need to stress to

absolutely use the GitHub repository or

web3 dev. education associated with this

course if you're on the GitHub repo

right now and you scroll down to lesson

two and this is going to look a little

bit different when you come to it you

can click on the GitHub repo associated

with this lesson this will have all the

code that we're actually going to be

working with for this section as well as

a read me section which is going to have

a lot of notes on how to actually work

with the code and instead of making

issues and discussions on this

repository here if you have an issue

please use the discussions tab of The

Foundry full course here or use any of

the areas that we've laid out in the

questions section we're going to teach

you how to ask questions so that they

have the highest probability of being

answered by either somebody else in the

community by an AI or by a forum

additionally please be sure to check out

web 3d. for more information as well I

highly recommend that you pause the

video right now and make accounts for

first of all GitHub and then at least

stack exchange ethereum additionally

chat gbt is a great resource to make an

account for just remember that it will

often get things wrong and isn't quite

up to date find you don't need to make

an account for but it often gets things

wrong sometimes as well typically for

each coding section I'll give you a

brief rundown of what we're actually

going to be building and in this lesson

we're going to be building this exact

smart contract and we're going to be

building your first smart contract ever

and we're going to deploy it to a

blockchain at the end of this section

you are going to have deployed your

first smart contract ever so be sure to

get to the end so you can deploy your

first smart contract we're going to be

using something called an IDE called

remix to deploy and interact and work

with this smart contract which is going

to be very exciting it's highly

recommended to get the best experience

out of this is for you to follow along

and you to code with me you can change

my speed on the YouTube video if I'm

coding too fast or I'm coding too slow

but you taking the time to write out the

code as I code along with you is going

to ingrain the knowledge into your brain

repetition is the mother of skill and I

want to make sure you come out the other

side with skill actually code this we're

going to be using a tool called remix

you can either Google search it or you

can just come to the GitHub repo or web

3d. education and click this link to

remix which will pop open the remix web

ID so let's go ahead let's jump in and

let's learn to deploy our first smart

contract at the end of this lesson you

will have deployed your first smart

contract you'll have written your first

bit of solidity and we are very excited

to get through this

part welcome to the remix IDE or the

integrated development environment this

is where we're going to learn to write a

lot of our code in the beginning if you

want you can go ahead and accept to help

out remix here and if you've never been

to the remix website before it'll give

you a tutorial walkthr of some of the

features that remix has to offer for

example it has a solidity compiler

solidity is the programming language

that we're going to be using in this

course to code our smart contracts where

and we need to compile them when we've

written the solidity we'll learn about

that in a little bit we have a tab here

where we can actually deploy our

contracts to a blockchain and we have

all these different folders and scripts

since we can actually write JavaScript

and typescript in remix as well but

don't worry about those too much for now

because I'm going to be explaining

everything that we're going to do remix

is an incredibly powerful tool because

it has a lot of features that will allow

us to really see and visualize what our

smart contracts do eventually we're

going to move off of remix to a local

development environment however remix is

a tool still used by some of the top

Auditors and smart contract developers

in the space when they want to quickly

check something out and additionally

it's fantastic for learning the

fundamentals of solidity the left hand

side is where we're actually going to

start interacting with remix if we bring

our Mouse up to the top this little file

explorer is where we're going to have

all of our files and where we're going

to write our solidity or our smart

contract code if you want you can leave

all these folders in here but I'm

actually going to go ahead and delete

everything so that there's less for me

to work with or or deal with so I'm just

going to go ahead and rightclick and

delete everything in here just so I can

start completely from scratch again if

you want to leave all of these in here

feel free to do so doesn't matter I just

think it's cluttering up my mental space

a little bit now we have a blank remix

project and the first thing that we're

going to want to do is create our first

file to start writing and deploying our

solidity smart contract we're going to

go ahead and click the create new file

right here and type in simple storage.

Soul doou tells our compiler that this

is going to be a solidity contract a

solidity file and we're going to be

writing solidity inside of this file

which again solidity is the most popular

smart contract programming language and

you'll see we actually get popped up a

simple storage. Soul on the right hand

side which you can type in and actually

write our solidity code now right below

the file explorer button is a little

search icon which allows us to search

for different code in all of our

contracts so for example if I type in

hello in here and I copy that paste that

into the search bar hit enter we can see

that it found this line hello in our

simple storage. let's go ahead and

delete that right below that search icon

is this solidity compiler and you'll see

a bunch of different stuff pop up which

tells us about our compiler

configuration and we can see even more

advanced configuration if we hit the

dropdown we're not going to hit that for

now let's go ahead and double click this

solidity compiler over here so we can

just see the simple storage. soulle I'm

also going to click this hide terminal

button so that we just see our simple

storage. soulle now the first thing that

we want to do in all of our solidity in

smart contracts is write the solidity

version that we're going to be working

with solidity is a constantly changing

language and we want to be very specific

about what version we're going to be

using to write our smart contract as

each version does different things to

write your version you're going to do

pragma solidity and then type your

version for most of this course we're

going to be using

0.819 as that's the most current

addition of solidity however getting

used to working with different versions

of solidity is really good for you as

you're going to be working with

different versions of solidity no matter

where you go certain versions of

solidity are considered more stable than

other versions right now there's a

popular tool called Slither which

recommends using

0.818 so if you want to default to 0.818

for this course feel free to do so we're

going to be using a couple different

versions as we code so this line says

we're stated our version now these two

slashes here stand for what's called a

comment in solidity and this allows you

to write anything after the two slashes

and when we compile or run our code it

will just ignore what's in here so we

could type blah blah blah whatever we

want cats are cool and it doesn't matter

you can write anything in here I highly

recommend as we're going along you

should write comments in your own code

as well for you to refer to later on and

additionally feel free to copy all the

code that you write and paste it locally

so that just in case your browser cache

refreshes or something you won't lose

all the work you've done so so before

you lock off for the day copy paste this

into a text file so that you can have it

for later but a good comment for here

might be this is the version now writing

our version like this in solidity tells

the solidity compiler that we're only

allowed to use 0.818 when compiling this

however maybe a new version comes out

and we're okay to use anything newer

than this version to tell the compiler

that we add this little hat this little

carrot which says this contract only

works with

0.818 or anything greater than that this

means 0.8.9 would work when 0.820 comes

out that one would work however

0.817 would not work if we were working

with 0.818 or above if we don't have the

carrot this tells the compiler that only

0.818 will work with this code if we

want to use solidity versions within a

range we could do something like this we

could say we want our version to be

greater greater than or equal to

0.818 but less than

0.9.0 this would tell the compiler that

any version between these two is a valid

version for example

0.9.1 would not work neither would

0.9.0 because these are not strictly

less than

0.9.0 great so now we know how to do

compiler versions now the next thing

every smart contract needs to start with

is something called the spdx

license identifier now this actually

isn't required by the compiler it'll

actually throw a warning if we compile

and it won't error it's fine if you

don't have this however it's highly

recommended this is a way to make

licensing and sharing code and IP of

your contracts a lot easier from a legal

perspective I have a link to more about

how licenses work in the GitHub repo

associated with this section of the

course MIT is known as one of the most

permissive licenses it basically means

anybody can use this code and pretty

much do whatever they want with it I

wouldn't worry too much about the

licenses right now but let's actually go

back to

0.8.9 and on the left- hand side let's

scroll down to this compiler button and

open this back up even right now now

that we don't even have any code we can

actually go ahead and compile this

contract now you might see a red

squiggly and you might see a warning

here but don't worry about that for now

to choose our compiler version We scroll

up to this section and we can choose the

compiler version that we want to work

with most of the time though if you just

hit compile simple storage. soulle or

you hit this big compile button it'll

automatically choose the version for you

for example if I scroll down but I hit

compile it'll automatically flip up to

08.19 and we were able to go ahead we

were able to successfully compile this

code now it says no contract compiled

yet because we haven't put a contract in

here yet we just put the version of

cility that we're working with compiling

our code means taking our human readable

code and transforming it into to

computer readable code which is

essentially a bunch of zeros and ones or

it's bite code computer code is very

specific instructions for the computer

to use or in our case the blockchain to

use for our contract we'll learn later

about Machine level code and op codes

and evm codes in a much later section of

this course Additionally you can hit

command s or controls which will also

save and compile you'll see I kind of

have a trigger finger and I will out of

habit hit command s all the time

because as somebody who codes a lot I

need to make sure I save all the time

otherwise things might not work as

intended as you saw if we use a

different version of solidity and we hit

the compile button it'll automatically

flip back but for example let's say I

wanted to use

0.8.7 anything greater than that and

we're on compiler

0.8.9 and we hit compile it won't change

however if I use something less than

0.8.7 and we hit compile it'll change

because it wants to automatically select

a solidity version that is appropriate

for the version that you chose again I

want to use

0.818 and I'm going to hit compile and

we're good to go now we're going to go

ahead and start writing our contract and

to get the full screen view again we

just go ahead click the solidity

compiler so that we can just see our

code here to start writing our contract

we're going to use a keyword in solidity

called contract this tells solidity that

the next piece of code is going to be

the name for our contract that we're

going to create you can think of a

contract very similar to a class if

you're familiar with JavaScript or

python or Java or really any

object-oriented programming and we're

going to go ahead and give our contract

a name here we're going to call ours

simple storage and then we add this

little open and closed curly braces or

curly brackets everything inside of

these curly brackets is going to be

considered part of this contract simple

storage now if we hit enter we go back

to the compiler and hit compile we can

see once again this little green check

Mark pop up this means our compilation

has been successful if we were to remove

for example this curly brace and hit

compile we would see we would get this

error compilation failed with one error

and if we scroll to the bottom it'll

tell us where the error actually is and

we'll get a little red popup saying what

line the error is actually on we'll

learn about debugging these errors in a

little bit but let's add the curly brace

back go ahead back to the compiler

compile and we're good to go

hypothetically we could deploy this

smart contract right now this is a valid

contract although it doesn't do anything

but congratulations technically with

just this little piece of code you've

written your first smart contract I

spelled version wrong so we're going to

correct that city has many different

types of things that you can build in

these smart contracts many different

data types or just types if you go to

the solidity documentation at docs.

solidity l.org again link this in the

GitHub we can select the types section

on the left hand side to learn more

about solidity types if you want to get

a holistic view of all the different

types you can go ahead and read this

documentation some of the basic types

are going to be Boolean Boolean uent and

an address and bytes bytes is a lower

level type which we'll talk about in a

little bit a Boolean is some type of

true false value a uint is going to be

an unsigned integer AKA a positive whole

number meaning no decimals no fractions

a integer is going to be a signed whole

number meaning it could be positive or

negative but again is a whole number and

then we have an address which is going

to be well an address it's very similar

to if we open up our metamask and we

click this account here it's going to be

something like this there are some other

types as well and ways to create your

own custom types but we'll learn more

about that later on we can use these

different types to Define different

variables VAR variables are essentially

holders for different values and these

values can have one of these types for

example we could create a variable

called has favorite number which would

represent if somebody has a favorite

number this has favorite number could be

true or false either they do have a

favorite number or they don't to tell

solidity that this has favorite number

is a true false or a Boolean we would

add this Bull keyword before has

favorite number so this has favorite

number is going to be either true or

false and to set its value we're going

to give it this little equal sign and

say true so now has favorite number is a

variable that represents true we could

also say has favorite number is false

meaning that somebody doesn't have a

favorite number for a uent which again

is an unsigned integer we could say uint

favorite number equals 88 this means

that this variable favorite number is

going to be 88 a uint and int are

actually special in that we can actually

specify how many bits or bytes that we

want to use for example we could say U

256 U 256 specifies this variable

favorite number has 256 bits we're not

going to go over bits and bytes in depth

right now but if you want to get a quick

refresher we've left a link in the

GitHub repo associated with this course

to give you an overview of bits versus

bytes and how they work an easier way to

think about this is really just how big

can it get the bigger the number over

here the bigger this favorite number can

be the maximum size is a ENT 256 and if

you don't specify the U 256 it defaults

to being a u 256 so this and this are

the same thing this this same thing you

could also have 8 Bits 16 bits 64 bits

Etc often times it's better when we're

writing our code for a readability

standpoint to be as explicit as possible

so you'll see me pretty much always

writing U and 256 because I want to be

very explicit with how many bits I'm

using for U and 256 even even though

they mean the same thing instead of a u

256 we could also have this be an INT

256 and actually let's add that Boolean

back up here now an INT can actually be

positive or negative so we could have

our favorite number be88 if we wanted to

we can also have strings or text

variables which I didn't name up here

but I'll say why in just a minute we

could say string

favorite in text equals 88 let's

actually make this positive 88 even

though an INT could be positive or

negative I'll put this little semicolon

here you'll notice that at the end of

every one of these lines I'm adding this

semicolon the semicolon is how you can

tell solidity that a statement has

completed so this semicolon is saying

the end of this line is right here if we

wanted to we could put all of our code

on the same line like this and this

would compile fine it just looks really

ugly so we always want to put our code

on a new line after the semicolon a

string in solidity

is basically text that represents well

words so I could say 88 instead of

having 88 in here to tell solidity that

something is a string you have to put it

in between quotes I could put really any

combination of characters in here even

like hello or follow Patrick on Twitter

and let's actually do U in 256 here

favorite number and we'll do an in 256

favorite int equals 88 this way we'll

just have an example of all these

different types on screen we can also do

an address so we can say address my

address equals and we can go into our

metamask copy the address and paste it

right into remix and add that semicolon

and now we have our address type in

remix and then finally down here we're

going to say a bytes 32 object fav bytes

32 equals cat and we're going to put it

in quotes just like we did the string up

here and what's interesting about the

string object is that strings are

actually secretly just byes objects

specifically for text so a string can

actually get converted to a byes object

really easily because under the hood

they're essentially the same thing bites

typically look like something like xerx

and then a whole bunch of random numbers

and letters that represent the hex of

whatever the bites is and can often be

represented as strings like cat we'll

talk about btes more in the future

similar to U 256 and in 256 you can have

different size bytes like bytes 2 two

byes byes four byes 8 Etc all the way up

to 32 you can also have just straight up

bytes and not have a number after but

that's a slightly different type and

we'll go over that later as well a u

like this and a u 256 are the same thing

but a byes 32 and a byes with nothing

are actually different so keep that in

mind for now the largest bytes like I

was saying is actually 32 so for example

we can't do 8 bytes 64 and if we type

that in Here remix section goes hey

there's an issue here and if we try to

compile this we scroll down we'll again

see this little error code here and this

little error pop up it even gives us an

output declaration error identifier not

found or not unique it gives us the line

and we can say ah Whoops a Daisy this

should be a bytes 32 and we can go back

and compile this for our simple storage

contract let's say that we only want to

store a favorite number this contract is

going to be a contract that allows us to

store our favorite number and some

different people's favorite numbers as

well so we're going to go ahead and

delete everything except for the U 256

favorite number so we're going to go

ahead and delete everything and boom and

we'll pick a smaller favorite number

just to make it a little mentally easier

now these variables actually have

default values so for example if I don't

set my favorite number to anything and I

have a line that looks like this you'll

see that this actually compiles fine

favorite number will actually get

defaulted to zero and all of these types

have a different default value U 256 is

zero booleans is false Etc so saying U

256 favorite number and not having an

equal sign after here is the same as

doing U and 256 favorite number equals z

so for now let's not initialize it to

anything so that favorite number starts

off as zero and remember as you're

coding along here and typing along with

me if you get confused make sure to

write your own comments for example we

can say favorite number gets initial

ized to zero if no value is

given now let's go ahead and learn to

make our first function basic solidity

function section functions or methods

functions or methods are a subsection of

code that when called will execute a

very specific small piece of our entire

codebase if you're familiar with

JavaScript or python or any other

programming language functions in

validity are exactly the same functions

are identified by the keyword function

let's create a function and name it

store and we're going to have this

function be responsible for actually

updating our favorite number we're going

to store a new favorite number so you

first write the function keyword the

name of the function and then you add

these two parentheses whatever is in

between these two parentheses represents

what we're going to pass or send to our

function or the parameters that we're

we're going to send to our function for

example we need to tell our store

function what value it should use to

update favorite number so we're going to

tell our store function it should take a

un 256 and this variable that we're

going to pass to it we're going to call

underscore favorit number it's important

that we give it a different name than

favorite number up here and we'll talk

about that in a little bit then we're

going to say this is going to be a

public function and we'll explain that

soon too we want to put these little

curly brackets in here as well and we're

just going to say favorite number equals

underscore favorite number and without

going too deep into what this is doing

we're saying I'm not going to explain

public yet but we will in a minute but

what we're saying is whenever you call

this store function you're going to set

our favorite number variable to whatever

variable that we passed I'll explain why

we do this underscore here as well in a

little bit and with just this we can

actually start to simulate what this

smart contract will do and if our store

function will actually work correctly so

what we can do with just this code right

here is come over back to the compile

Tab and hit compile make sure that we

get this green check mark and that

everything looks good and then we can go

down to this deploy and run transactions

tab our deploy and run transactions tab

has a ton of different parameters in

here on how to actually deploy and run

with our transactions we're going to

deploy this contract to a simulated

virtual environment so we're going to

deploy it basically to a fake

environment we're not going to be

deploying it to a test net we're going

to deploy it basically in kind of an

imaginary world in order for us to do

this first make sure we're on this remix

VM and for us we're going to just use

the default which is the merge doesn't

really matter which one you're on just

so long as it's the remix VM this remix

VM is a fake local blockchain where we

don't have to wait for transactions to

complete and we don't have to deal with

any of the oddities on deploying our

code to a real test net or a real main

net and don't worry about the rest of

these for now we also get an account

here when we run on our fake remix VM we

get automatically given an account with

a different amount of ethereum for each

account you can think of each one of

these accounts similar to our metamask

accounts in metamask except for these

our fake imaginary accounts that remix

just gives to us for our transactions

including deploying contracts we're

given a gas limit values that we can

send and we can also choose our contract

depending on which one we've compiled

since we only have one contract in here

we only have one to choose from so on

the left hand side to deploy our

contract to this fake remix VM

environment we're going to go ahead and

collect the deploy button if we scroll

all the way down to the bottom now under

this deployed contracts we can see we

actually deployed a contract here simple

storage we can see the balance of zero

and we see this big orange button that

says store and then u56 favorite number

on our local blockchain this at blah

blah blah here this is going to be the

address of our contract similar to our

wallets how they have different

addresses every single contract has a

unique address as well and if we hit

this little copy button and we close

this we put as a comment here and we

paste it we can see this looks exactly

similar to an address such as what's in

our metamask and then let's go ahead and

open the deploy back up and we see that

deployed contract is still there

additionally if you hit this little show

terminal button and you pull this up we

can actually see we have this little

comment here creation of simple storage

pending and we have this green check

mark here this is notating that we

actually sent a transaction to deploy

this contract similar to sending eth

back and forth in order for us to deploy

a contract we actually have to send a

transaction since we're doing this on

the remix M this is a simulated

transaction a pretend transaction inside

of our remix environment you can even

hit the little drop down and see even

more information about this transaction

you'll see a lot of familiar keywords

like status transaction hash from to gas

Etc deploying a contract uses the exact

same process as sending a transaction

for just eth the main difference is we

populate this data or input field with a

ton of that bite code and if you copy

this input field or this data field and

go ahead and make a comment in here

you'll see it's a massive line and this

massive line notates all the data

associated with this smart contract all

the machine readable code remember

anytime we do anything that modifies any

value on the blockchain we actually do

that by sending a transaction deploying

a contract is modifying the blockchain

so we do it in a transaction which means

yes we spend gas now this big orange

button over here actually resembles our

function store in our smart contract and

if we add some numbers in here and we

call it again if we pull the terminal up

we can see transact to simple storage

pending and we see we sent a transaction

which called this store if we do this

again with a different number we call it

we can see our terminal say oh you sent

another another transaction to update

the state of the blockchain and if we

scroll all the way up to our account

you'll see that we have a little less

ether in our account because we had to

spend the gas associated with well a

deploying this contract and then B

calling these functions and then for

example if I add this if I add five in

here and hit store we'll send a

transaction to store five on the

blockchain now you might be thinking

okay Patrick that's pretty cool but what

is the value of favorite number you're

telling me that this function store is

up updating favorite number but I can't

really see it how do I know that

favorite number has actually been

updated to five well the reason we can't

see it is that the visibility of our

favorite number is actually defaulted to

internal so us not having anything here

or right internal are actually meaning

the same thing and we'll talk about

visibility and default visibilities in a

minute but in order for us to actually

see the value of our favorite number

we'll go ahead and add the public

keyword to this this changes the

visibility of favorite number to public

and like I said we'll talk about

visibility in a minute but let's go

ahead and compile this let's go ahead

and delete this contract by hitting this

x here and let's redeploy this contract

with this new public keyword so let's go

ahead and hit deploy and now if we

scroll down and we open up our simple

storage we actually now see a blue

button labeled favorite number and if we

click it now we can see it returns zero

which makes sense because we know that U

256 is default to Z now if I go ahead

and add five into here and hit the store

button if I pull up the terminal we'll

see that we went ahead and executed that

store function call that transaction

that's going to take input this five as

favorite number and set it to our

favorite number now if I hit favorite

number you can see it does indeed return

five showing that we actually updated

our favorite number with this function

call and remember though I'm going to go

ahead and do the skan and remember when

I hit X here this is just removing it

from this window here if you actually

deploy a smart contract to the

blockchain hitting X from this window

doesn't do anything because once you

deploy your contract it's immutable it's

out there and you can't just delete it

by clicking X and remix functions and

variables can have one of four different

visibility specifiers in solidity public

private external and internal if you

don't give one of these keywords to your

variables it'll get defaulted to

internal public functions mean that

they're visible externally and

internally and you'll see here it says

it creates a getter function for storage

slst State variables this means that

other people can call this function or

call this variable when we didn't have a

visibility for favorite number it

defaulted to internal which is why we

didn't see this blue number pop up

because internal it means that other

contracts and people aren't allowed to

call on this favorite number we have a

little bit more here it says it actually

creates a getter function for storage SL

State variables when we add this public

keyword here it's actually equivalent to

us making a getter for this favorite

number variable a getter function and

I'll show you exactly what the function

will look like in a little bit now keep

in mind though everything on chain is

technically public so setting a function

or variable to private isn't a good way

to hide what the value actually is there

and we'll talk a little bit more about

storage and visibility and and that much

later just remember everything on these

evm chains is actually public data this

public variable just means any other

contract can call this favorite number

and see the value what's in favorite

number and private means only the

current contract can external functions

mean they're only visible externally and

this is only for functions not for

variables and it means another function

inside this contract couldn't call an

external function and internal means

only the current contract and its child

contracts can call the function we'll

talk about child contracts and

inheritance in a later section so let's

just keep it public for now the reason

that we have this underscore here in

this parameter is because we need to

tell users that this variable in here is

different than favorite number and

there's a a couple different conventions

on naming local variables versus these

what's known as state variables or

variables outside of functions and we'll

go over those later in the course now

here's something that's really

interesting as well remember how I told

you earlier that sending ether is a

relatively simple transaction right well

let's see what happens when we call this

store function and we update favorite

number to five let's actually call it

one more time and we hit the little drop

down here let's go to gas and we'll see

gas actually cost 27,000 gas which is a

lot more than the 21,000 gas it costs to

just send ether between accounts

remember every time you update the state

of the blockchain it's going to cost gas

now what do you think will happen if we

do more inside of this store function

for example we say favorite number

equals itself + 1 let's go ahead and

compile this let's delete our old simple

storage let's deploy this new one

remember the last one cost 27 gas let's

pull up the terminal and remix actually

gives us a little tool tip and it's

saying an infinite gas which we know is

actually wrong but let's go ahead and

add one two 3 in here and we'll hit

store we'll see this transaction we'll

scroll down we'll see gas is actually a

lot more it's way more gas it's 50,000

gas with just adding this line here now

technically I'm not telling the full

story here because there are some other

gas costs associated with the first time

you run a function but it's still more

right and that's what's important here

so so let's go ahead and delete that

line and go back to our old function

here now let's talk about something

called scope for a second so if I create

a variable in here called U 256 test VAR

equals 5 and I create a new function

called something make it public could I

access the test bar and then maybe

change it to six or seven what about the

favorite number VAR what about the

favorite number variable could I access

that to seven well let's go ahead and

see what happens if we try to compile

this we try to compile we actually go

ahead and get an error in our

compilation Undeclared identifier

whenever you create a variable it can

only be viewed in the scope of where it

is if that's confusing just look for the

curly brackets the reason that our

something function can read the testar

is because this testar isn't inside of

the curly brackets of something the

reason it can't read the testar is

because testar was created way up here

inside of these curly brackets outside

of something but favorite number wasn't

created inside of these curly brackets

so how come it knows what favorite

number is well something is inside of

these curly brackets and favorite number

was created inside of all of these curly

brackets if favorite number was created

inside of here it wouldn't be able to

access favorite number because again

favorite number is inside of this scope

and not this scope if you create a

variable like testar inside of store you

can only access this testar inside of

this store function and not anywhere

else the easy way to know what the scope

of a variable is is just look for the

curly brackets so let's go ahead and

delete this something variable and let's

delete this test far and let's recompile

now like we were saying earlier when we

add this public keyword to favorite

number it's the exact same as if we

created a getter function to return this

favorite number so let's actually write

a function similar to what this public

keyword is creating so we're going to

say function retrieve make this a public

view function and we'll talk about that

in just a second and we'll say it

returns a uint 256 and we'll add the

curly braces here and we'll say return

favorit number and often times when

these Auto suggestions come up like this

you just hit enter and they will

automatically do it so if we do favorit

and then I just hit enter boom

automatically like that now I'm going to

hit command s which is equivalent to me

going to the compile Tab and hitting

compile now if I go to the deploy Tab

and let's deploy this contract now we

scroll down we now see we still have

that store function we have our favorite

number function and we have a new blue

button called retrieve right now they

both start off as zero and then

obviously if we update this to five by

calling store yep I called store these

now both return five since favorite

number is the actual variable and

retrieve is just returning whatever

favorite number is now as you can see

here these two functions are blue but

this one is Orange what's the difference

why are the colors different well the

key is actually with this view keyword

here solidity has a special keyword

which notates functions that don't

actually have to run or don't actually

have to send a transaction for you to

call them and those two keywords are

going to be View and pure a function

marked view means we're just going to

read state from the blockchain for

example in our retrieve function we're

just going to read what the favorite

number variable is our store function

isn't reading it's updating something so

and it's changing the state of the

blockchain so we have to send a

transaction since our retrieve function

doesn't have anything inside here that

updates anything it just returns

favorite number we don't need to send a

transaction so if you add this view

function in here it disallows any

modification of State for example I

couldn't add favorit number equals

favorit number + one if we go ahead and

try to compile this we'll get an error

function cannot be declared as view

because this expression potentially

modifies state so we'd have to remove

this line or we'd have to remove the

view keyword so view functions disallow

updating State your functions disallow

updating State and they disallow even

reading from state or storage this

favorite number here is what's known as

a storage variable because it's stored

in a place called storage we'll talk

about that in a later section but if

this was labeled pure we'd see we get a

little red underscore here because

favorite number is reading from State

instead of returning favorite number we

would return something like seven so

this would be an example of a pure

function this would be an example of a

view function because we're reading from

State again we'll explain the difference

a little bit later and like I was saying

before if we call a view or a pure

function we actually don't need to spend

gas since we're not modifying the state

that's why these buttons over here are

blue they're representing view or pure

functions functions that we can call

without having to send a transaction for

example if I pull up the terminal here

and I pull this up and I call retrieve

we do get another function but it's just

a call and it looks different than if I

hit the store which has this little

check mark they're different because the

store is obviously sending a transaction

and the retrieve is actually just making

a call and not sending a

transaction however something weird is

going on here if I hit retrieve and I go

into the details of this call I can see

oh what's what's this why is there an

execution cost it says cost only applies

when called by a contract what's going

on there the reason for that is because

if another function that does update

state that does require a transaction

calls retrieve that transaction does

need to pay the gas of reading and

calling this retrieve function so

calling a view or a pure function

actually does cost gas only when a gas

cost transaction is calling it so we can

go ahead and call these as much as we

want it costs nothing but if another

function that does cost gas calls it

it's going to cost something for example

if our function store here then went

ahead and called retrieve like this

since store cost gas you're telling this

function hey also call this retrieve

function which is more work for it to do

and since it's more work it's going to

cost more gas so for example if we

delete this contract over here let's go

ahead and compile this let's go ahead

and deploy this with this retrieve in

here so let's go ahead and look at these

These are now zero we'll store five in

here we'll select the drop down we can

see how much gas we actually sent 50,000

gas let's go ahead and drop this now

close this out let's remove the retrieve

line let's compile we'll hit deploy

simple storage these are both zero We'll

add five it's store pull up the terminal

hit the drop down look at gas it's still

$50,000 but it's actually a little bit

less than before although I'm pointing

at gas we really should be looking at

transaction cost because gas is really

just actually how much we're sending

whereas transaction cost is how much gas

the transaction actually cost but in any

case it was a little bit less without

the retrieve function now I've kind of

been glossing over this a little bit but

this returns keyword specifies what this

function is going to give us when we

call it so when we have this returns

keyword in our retrieve function here

we're saying whenever we call this

retrieve function we want to get

returned or we want to be given this

favorite number of Type U 256 we want to

return a unu 256 from this

function now our contract as is is

pretty good it does one thing pretty

well it's it allows us to store our

favorite number update that favorite

number and then view that favorite

number and in fact let's go ahead and

make this an internal variable and we'll

have the retrieve function be the way to

get this we can have this public but for

now we're going to set it up like this

and I'll tell you why we're going to set

it up like that in the future but what

if we wanted to be able to store not

just our favorite number but other

people's favorite numbers as well well

what we could do is we could create

something called an array or a list of

favorite numbers what we could do is we

could say instead of just one uent 256

we could have a list of un 256 called

list of favorite numbers this bracket

syntax here identifies that we have a

list of un 256 or a list of numbers or

an array of numbers an array of numbers

is going to look something like this

it's going to have maybe the first

element is going to be zero maybe the

second favorite number is going to be 78

maybe the third favorite number is going

to be 90 now arrays are very common in

computer science and programming and an

array in solidity is exactly the same as

an array in any other programming

language if you're unfamiliar with

arrays arrays or lists are actually zero

indexed so the zero here is actually at

index zero so we refer to this object

here as the zero withth object right

this could be 77 and this would be the

zero withth object the 78 is going to be

the first element the 90 is going to be

the second element and so on and so

forth it's very common in computer

science to actually start counting from

the number zero and arrays start

counting from the number Z we'll learn

to play around with arrays more in just

a minute so this list of favorite

numbers is great but how do we know who

favorite number each section is this is

our list of favorite numbers how do we

know who zero is who 78 is who 90 is ETC

well maybe what we would do instead of

just having a raw list like this let's

go ahead and comment this line out maybe

we could create a new type called a

person in solidity you can actually

create your own types using the struct

keyword so we're going to say struct

person and do little curly brackets like

this inside of these curly brackets we

can Define what this struct person

custom type is comprised of and we're

going to say for every person they're

going to have a u 256 favorite number

and a string name now something

important to note is oh whoops we have

two favorite numbers here remember what

we learned about scope since this

favorite number is inside of these curly

brackets these would Clash a little bit

so what we're going to do instead is

we're going to rename favorite number up

here to my favorite number and we're

going to copy paste that down here as

well so we're we're renaming this state

variable this storage variable to my

favorite number and just keeping it down

here that way we can have favorite

number inside of this struct in any case

we created this new type of type person

which is a combination of each person

has a favorite number and each person

also has a name now similar to how we

can have a u 256 a Boolean a string and

in 256 Etc we now have a type of person

and this is similar to each one of these

oh and we're also going to have to

update the retrieve down here with my

favorite number instead of favorite

number now since we have our own new

type we can actually create a variable

of type person the exact same way we

created a variable of type my favorite

number so we could say person visibility

will be public my friend equals and

we'll put person here and put some

parentheses here because when you're

working with custom types you have to

Define both on the left side and on the

right side what type it is and in here

we would assign a favorite number and a

name so we could say seven and Pat like

that so now Pat is going to be a person

with a favorite number of seven and a

name of Pat see the first parameter goes

to the first

item in the person struct and the second

parameter goes to the second item I like

being a little bit more explicit when

working with structs and actually what

you can do is you can put little

brackets here instead and you can say

exactly what value you're going to

assign to what section so I can say

favorite number is going to be seven and

name is going to be that and we can hit

command s or just go straight to compile

to see if it worked correctly get that

little green check mark Now by doing

this we've created our own type person

and we've created a variable named Pat

with a favorite number of seven and a

name of Pat now if we were to go ahead

let's delete this old simple storage and

let's deploy our new simple storage we

scroll down we now have a new blue

button since this is a public variable

called Pat and if we click the button if

we call this variable we'll see favorite

number of seven and string name Pat you

can also see this zero and this one

which shows the index of each one of

these variables or parameters zero is

for favorite number one is for name if

we added another one maybe bull is cool

bull is cool would be at index 2

whenever you create a custom type like

this solidity will automatically index

them similar to the way that we index

our list or our Rays favorite number

zero name one whatever is next would be

two EX Etc now this is great for one

friend but what if you have a lot of

friends which I know a lot of you do

because you're taking this course which

automatically means you're cool maybe

what if you have your friend Mariah that

you would like to add to our smart

contract like this and her favorite

number is 16 or maybe your friend John

you'd have to copy paste the line add JN

in here his favorite number is going to

be 12 so on and so forth it might get

very tedious to have to write variables

for all of these people for all these

friends this obviously isn't a great way

for us to create lists of people or

lists of our friends so instead of this

we can actually use this array syntax

that we just learned and create an array

of person or a list of persons so I'm

going to comment all these out for now

and a quick tip here if you're on a Mac

and you highlight a couple if you're on

a Mac and you hit command backslash or

command question mark it'll

automatically comment or uncomment those

lines if you're on a Windows I believe

it is control slash but you might be

able to Google what the actual keyboard

shortcut is this is a keyboard shortcut

I use all the time so what we're going

to do now is we're going to create a

list or an array of persons so exact

same as we did it up here we'll say our

type first is going to be type person

array so we're type person array then

we'll State our visibility which is

going to be public then we'll get our

variable name which is going to be list

of people like this so we've created a

person array with visibility public and

the name list of people and we'll just

leave it blank for now so it'll get

defaulted to being an empty list which

would look like this now if I were to go

ahead and deploy this let's delete the

last one let's compile deploy we scroll

down we select this we now see we have

our retrieve blue button and we also

have this blue button for list of people

when you create arrays with a public

keyword

instead of being able to see the whole

array with this list of people button

you actually have to put in the index of

the elements you want to work with and

you get to see that exact element it

wants to take a u 256 as an input

parameter however obviously our array is

blank so if we say what is the person at

the zeroth index it'll say well nothing

because you have a blank array well what

about the first index well nothing what

about the second one well nothing no

matter what you put in the box right now

it's going to return nothing we'll show

you how to add to this array in just a

second this kind of array is known as a

dynamic array because the size of the

array can actually grow and shrink in

solidity a dynamic array is signified by

what's inside of these little brackets

here if we added a three in here this

would be a static array we're saying

this list of people can only have a

maximum size of three so we can only put

three persons in this array

Dynamic array static array can have any

size can only go up to three any size up

to three any size up to four hopefully

you get the picture we're going to work

with a dynamic array because we're going

to want to add a arbitrary number of

people to this person array so let's

create a function that will allow us to

actually add people and update this

array and let's delete this comment so

below our retrieve function we'll create

a function add person

and this is going to take two variables

as input it's going to take the name of

the person that we're going to add it's

going to take the favorite number of the

person that we're going to add as well

as the name so we'll say string memory

name and I'll explain this memory

keyword in a little bit and we'll do

uint 256 unor favorite number and let's

do and let's do underscore name and

we'll make this a public function and

what we're going to do inside of this ad

person function is we're going to take

this list of people object and call the

push function on it arrays come built in

with a function called push which allows

us to add elements or add person to our

list of people array so what we're going

to do is we're going to say list of

people. push and we'll add these little

parentheses here and we're going to push

a new person onto this array now what we

could do now let's comment this out for

now now what we could do is we could

create a new person person new person

equals person name favorite number like

we did above oops excuse me these are

backwards person memory new person which

we're going to ignore that for now and

then just do list of people. push new

person we could do this this is valid

syntax and I'll explain this memory

keyword in a little bit this is going to

create a new person and we push to the

list or we could just add this person

right into this push piece here so we

could delete this line instead of

creating a new person on its own line we

could say list of people. push person

and then we'll add in here favorite

number name since we're calling this

person favorite number name inside of

this push object solidity is smart

enough to execute this line of code

first create a new person and then

execute this line to push our person

into this list of people object so this

function should allow us to push new

people into our list of people array so

what we can do now is let's compile this

let's deploy this let's delete the old

one we'll hit

deploy now we see if we call our list of

people at zero we'll get nothing back

because it starts off as a blank array

but now we have this new add person

function where we can you can kind of

see very faintly it takes a string name

and a un 256 a favorite number so we can

add Patrick 7 we'll hit add person which

if you have your terminal you'll see we

made a transaction and now if we hit

list of people at zero we see we have

indeed added a person to the zero withth

index Patrick has a favorite number of

seven and his name is Patrick obviously

if we hit one we'll get nothing back and

this will just stay up but if we add

another person maybe John 16 add person

now at list of people index one we now

see John 16 so 0o it's going to be

Patrick 7 1 John 16 2 is nothing so

nothing

happens now we've talked about this a

little bit already but if we go ahead

for example and maybe delete this

semicolon and we go to try to compile

and we scroll down you'll see we get

this error parser error expected

semicolon but got bracket instead and it

gives us this little red exclamation

mark and the line that it's having an

issue with all these red errors mean

that your code isn't compiling and you

can't actually deploy this to the

blockchain because solidity doesn't know

how to turn this human readable code

into machine readable code so we need to

add this semicolon here recompile so we

get no errors now interestingly though

if we go to the top and let's say we

delete this SPX license identifier and

now we compile we scroll down we get a

yellow box and it says warning instead

of error says warning spdx license

identifier not provided source file blah

blah blah interestingly though if we

compile this we actually let's delete

our last symbol storage we can deploy

this so something important to note is

warnings are just that they're just

warnings they won't prevent you from

deploying or compiling your code errors

will prevent you from deploying or

compiling your code now even with that

being said though it is good to try to

remove all of the warnings because the

warnings are generally there for a

reason they're warning you that you

might be doing something bad and

sometimes if you have a bug in your code

simply just listening to the warnings

would have solved it so it's best to

listen to the warnings here so to

summarize if it's red it's broken if

it's yellow you might want to check it

out and additionally when it comes to

these errors and These Warnings this is

where using our Ai and Google searching

skills can really come in handy let's

say for example I ran our code I get

this error I read the error and I don't

really understand what's going on here

what we can do is we could maybe copy

this error and use any of the search

features that we talked about resources

for this course we can use chat gbt or

find GitHub discussions stack exchange

ethereum and panum and I'll explain what

each one of these is good for later in

the course but for example let's go and

try out find find is an AI search engine

for developers what it does is it first

does a Google Search and then it reads

all those links links and based off the

links it reads it tries to give you an

answer so what we could do is we could

say I am getting this compiler error in

solidity how do I fix it we hit this

little dropdown put any code or context

here we'll paste our error this is the

error like this and we'll go ahead and

hit

search we get a pretty verbose response

on what's going on with our code we

could actually take this a step further

and we could copy our entire code base

and we could paste it under here we say

code I usually put three back ticks

before and after any code that I use and

I'll teach you why in the future well

let's go ahead and hit enter and

research it actually is able to read our

code and say one way to fix the error is

to Simply add a semicolon at the end of

the line where you push the new person

to the dynamic array list of people and

we can see if we do indeed get a way to

just copy our ad person function and we

can scroll down and just paste it on top

with it being fixed and we could also

say concise because it's being a little

too verbose for us we'll hit enter again

and it wasn't that concise but a lot of

these AI tools like I said are still in

beta but this was a good example of how

using an AI tool like this can actually

help you detect bugs like I said often

times they will still get things wrong

which is why it's important for you to

know about GitHub discussions stack

exchange piranha Etc later in the course

I'll explain more about how to ask good

questions how to do good AI prompting

how to format your questions and how to

search and learn more one of the key

pieces of being a really good software

engineer or a good prompt engineer is

less about actually knowing the

information and more about knowing where

to find the information so throughout

this course I want you to practice using

these resources because they're going to

help you be a much stronger developer

much stronger prompt engineer and just

be better at every thing that we're

going to go over in this course if find

or chat gbt gives you a poor answer be

sure to use the GitHub discussions if

you have a question specific to this

course be sure to use the GitHub

discussions or if you have a more

general question about solidity about

Foundry or anything like that you can

use one of these resources again I'll go

over this more later but great job

you've done your first bit of prompt

engineering

congratulations you don't have to

understand this section fully now one

thing that we didn't really go over and

we kind of glossed over was this memory

keyword and you'll notice if we actually

delete this keyword and you try to

compile we'll get an error data location

must be memory or call data for

parameter in function but none was given

now there are actually six places you

can store data in solidity you have the

stack memory storage call data code and

logs we're not going to go over all of

these areas right now but we are going

to go over some of the big ones which

are call data memory and storage and

this is going to be a little bit

Advanced here so if you don't understand

this section the first time don't worry

about it just keep pushing through it'll

make more sense as you go later on in

the course call data and memory both

mean that this variable is only going to

exist temporarily it's only going to

exist for the duration of the function

call any anytime we call AD person with

a different name we can only access this

name variable that one time that we call

this function if I call add name Patrick

7 and now I try to list of people at

zero obviously we see Patrick at

favorite number seven we can actually

never access that Patrick variable ever

again because it existed in memory it

existed for a very short period of time

just for that single call we could also

have call data here and we'll go ahead

remove this deploy the drop down and do

the same thing we'll add Pat

and actually you don't even need the

quotes Patrick do 88 add person we'll

see if it's in there sure is call data

and memory both mean temporary variables

inside of functions most variables

automatically default to memory

variables strings are a special type in

solidity so you have to specify memory

or call data and it has to do with the

way arrays work in memory but we'll talk

about that much later on the course now

the question obviously then follows okay

well if call data and memory are both

temporary variables why have two what's

the difference between these two well

let's try something let's have this be a

memory variable and in here we'll say

name equals cat so we're going to

reassign whatever people put in here to

Cat Let's compile this looks like it

compiles fine now let's do call data and

try to compile ah we get an error type

error type literal string cat is not

implicitly convertible to expected type

string call data the difference between

memory and call data is that

a memory variable can be changed it can

be manipulated if we pass a memory

variable to a function we can go

ahead memory and I hit and I hit command

s to compile this is valid solidity this

is not if you pass a call data variable

you cannot modify it call data is

temporary variables that cannot be

modified memory is temporary variables

that can be modified and storage is

permanent variables that can be modified

my favorite number was actually

implicitly converted to a storage

variable since it's added in this state

context outside of a function if you

create a variable that's outside of any

function inside of a contract it'll

automatically be a storage variable and

let's delete this line let's compile

let's deploy again delete this deploy we

know it's a permanent variable because

we can hit retrieve and we can always

access what is in favorite number so if

we store 1 2 3 we hit store or we can

hit retrieve and we can access 1 2 3 so

this variable 1 2 3 exists outside of

function calls now even though I said

there are more places like stack code

log return Etc we can only make these

variables call data memory or storage

and like I said we'll explain that later

in the course so let's go ahead let's

add this back to memory because that's

normally what you'll see now the next

question that logically follows is oh

okay Patrick well why do we need to put

memory here but we don't need to put

memory over here in fact if we try to

put memory there we'll get an error data

location can only be specified for array

struct or mapping types but memory was

given like I was saying earlier arrays

structs or mappings are considered

special types in solidity and the way

that memory management works under the

hood makes it so that we have to put

this memory keyword un 256 is known as a

primitive type and solidity is smart

enough to know where to put this

favorite number always under the hood

like we were saying earlier a string is

actually an array of bytes and so so as

we just saw with the air we need to put

the memory keyword for arrays so then

the next question is okay well what

about the storage variable can I put

that here no you can't put that here

either since this is a function solidity

is smart enough to at least know that ah

okay this is a temporary variable that

you're working with it's got to be

memory or call data it's not going to be

storage since this name is only going to

exist for a short duration so you got to

pick one of these other two so the

summary of this section is that strs

mappings and arrays need to be given

this memory keyword string is an array

of bytes so it needs this memory or call

data

keyword so this code is starting to

shape up it has a lot of functionality

here we can store variables we can add

people but it has a bit of an issue if

we have this contract and we want to say

oh what was Kelly's favorite number

let's say we have four people in the

array let's have Pat

7 John 8

Mariah

10 and Chelsea 22 or

232 and we asked the question ah what

was Chelsea's favorite number well the

way we would do it is we'd have to

actually Loop through this list of

people to find Chelsea so we'd say okay

what's at zero ah okay that's Pat that's

not Chelsea what's at two Ah that's John

what's at three Ah that's Mariah excuse

me what's at three Ah that's Chelsea

favorite number 232 okay perfect I found

Chelsea but obviously if we had a

thousand people in this array that would

be a very tedious process and that would

take a long time for us to find the

person that we wanted so the question

then is is there a better data structure

than a list or an array to use that

makes it much easier to access and find

the information about the people that we

want and the answer to this is using a

mapping you can think of a mapping as a

dictionary it's a set of keys with each

key returning a special set of

information about that key so it's

similar to a dictionary if you look up

the wordthe the wordthe will have a

whole bunch of text Associated only with

the word thee so let's create a mapping

type and you'll see how it works in

practice so we're going to create a

mapping like this with this mapping

keyword and we'll say the key is going

to be a string and It'll point to a uent

256 so this is going to be our type

obviously what comes after the type our

visibility so let's just go ahead and do

public for this as well and I like to be

very explicit with my naming so I'm

going to say name

to number signifying that this mapping

Maps someone's name to their favorite

number and now with this we have

essentially a dictionary where every

single name or every single string is

going to map to one number so for

example if we looked up Chelsea we'd

automatically get returned the 232 that

we're looking for instead of having to

iterate through this list so let's add

some capabilities to our ad person

function here so that we can update our

mapping so we have this list of people.

push which adds someone to the array

let's also update this so it will also

add somebody to our mapping to do that

we'll say name to favorite number and we

put these little brackets in here to

specify what the key is and we'll

saycore name and we'll assign that

toore favorite number what this line is

doing is now it's saying all right in

our mapping up here in our name to

favorite number mapping anytime you look

for that person's name you'll

automatically get their favorite number

back and now you have a much quicker way

to access people's favorite numbers just

by knowing their name so let's go ahead

let's compile

this let's deploy this let's delete our

old one we'll deploy

this now we have this new name to

favorite number blue button and so let's

go through the same problem so let's say

we have Pat 7

John

16 Mariah

32 Chelsea

232 now same thing list of people zero

returns Pat list of people one John so

on and so forth or we could just go down

here and let's say let's look up Chelsea

and we automatically get 232 we get

Chelsea's favorite number back

automatically same thing if we look up

Pat we get seven if we look up JN

we get Mariah and if we look up

cheesecake we get nothing back in a

mapping the default value for all the

keys is zero so if you look up a key or

a word that we haven't added in the

mapping yet it defaults to the default

value of whatever that type is since RS

is a string to U at 256 U at 256 default

type is zero if we look for a key that

we haven't added we get zero back

so now that we've added all this

functionality we're looking pretty good

we really like the way that our contract

is set up we have our my favorite number

which is a internal variable but we have

a way to read it with retrieve we have

our new typing person we have a public

list of people array we've got a public

name to favorite number got a way to

update the favorite number retrieve the

favorite number and add people to both

our list and our mapping now now in the

future you'll hear me say that you

should never do this before you write

any tests before you get it audited but

for now this is just a dummy contract

that we're going to deploy on a test net

so we don't really care but let's go

ahead and learn how to actually deploy

this to a real test net this is going to

simulate what deploying to a real

network with real money is going to look

like are you ready you should be this is

going to be incredibly exciting after

you do this successfully you should 100%

tweet about it on Twitter on LinkedIn on

lens protocol on whatever social media

you want it's important to celebrate

your small wins surprisingly it'll help

motivate you moving forward so first off

let's make sure this actually compiles

okay cool we've got a green chat Mark

there's no warnings there's no errors

fantastic now let's go back to the

deploy Tab and we'll delete this down

here and we'll scroll up and we're going

to change the environment we're in this

remix VM and we're actually going to

move to injected provider metamask

remember this remix VM is kind of this

fake world that remix gives to us

injected provider metamask means that

we're going to literally inject our

metamask into this remix we're going to

inject our metamask into this website

we're going to allow this website to

interact with our metamask we'll first

get prompted by metamask to pick the

account we want to use I'm going to use

account one and hit next and we're going

to go ahead and hit connect similar to

the way we connected to the faucet we

scroll up to our metamask we now see oh

it says your account is not connected

that's because I'm currently on account

two let's flip to account one and we do

indeed see that account one is connected

and now before where we saw kind of this

fake account with fake ether we see our

actual account with the actual amount of

sapoia e that we have make sure that

again be sure to use whatever

recommended test net we have in the

GitHub repo for us we're using sapoia

don't worry about the rest of these for

now so make sure you're on the correct

test net to deploy to a test net you're

going to need some seia eth so if you

haven't been to the faucet be to head

over to the faucet to get some suppo eth

remember you can find those in the

GitHub or web 3d. education now in remix

what we're going to do we're going to do

the exact same process we use to deploy

to the virtual remix environment we're

going to do that to deploy to the test

set environment so we're going to go

ahead hit the deploy button and metamask

is actually going to go ahead and pop up

this is similar to what we saw with the

blockchain example with signing

transactions we're actually going to

sign and send a transaction on the test

set it's similar again to us sending

ether to our ourselves the difference

here is though that our data section has

a ton of information here all this data

is associated with sending this

transaction but this one has all of this

contract information encoded in machine

readable code or our compiled code in

details we can see all the pavement

information associated with this

transaction we can see exactly how much

gas it's going to cost to deploy this

contract on chain but again we're on the

aoia test Network so this is fake money

anyways to actually deploy this we're

going to go go ahead and hit the confirm

button and now we're going to have sent

our function if you have the terminal up

you can see we have this call created

and it says creation of simple storage

pending with this view on ether scan

button if you click the view on ether

scan button you'll get brought to this

ether scan page with this transaction

going through on sepolia you'll see it's

currently being indexed by Ether scan

but there's a good chance it already

went through and back in remix it

actually goes ahead and gives us this

green check mark saying that we did

indeed deploy this contract

you might have to wait a few minutes for

this to complete because again we're

sending a transaction to a test net

blockchain and the blockchain needs to

actually ruce the block with our

transaction in it but if we wait a few

minutes on either scan we'll eventually

see a success status with block

confirmations on this block section here

and exactly the same as what we saw with

sending e to ourselves we see all this

information about the transaction

transaction hash status block time from

to blah blah Etc but if we scroll down

this input data field is much bigger

than anything we've seen before because

again this is all the data associated

with creating this contract and of

course we see more gas fee information

because again deploying a smart contract

to the chain is modifying the blockchain

so we have to spend gas now if we come

back to our remix and scroll down we're

able to see our simple storage contract

and we're able to copy the address that

it's at so if we copy this address we go

back to Ether scan we can even paste

this into the bar here and we can see

this contract that we went ahead and

deployed ether scan is smart enough to

know that this transaction created a new

contract remember this has to be on The

seoa Ether scan not the main net ether

scan because we sent this on the sepolia

testnet so now that we have this

contract created we have all the exact

same functions that we had in our

virtual environment but these functions

are actually on a test net with a

contract that we actually deployed now

we can do all the exact same things we

were doing on our fake remix environment

on this test environment for example we

can call retrieve which doesn't send a

transaction it just reads off the

blockchain

and we get zero same as what we got

before if we look up a name like Pat in

name to favorite number we get nothing

back cuz we haven't updated anything if

we add zero in here for list of people

we get nothing back as well metamask

didn't pop up here because these blue

buttons are view functions View and pure

functions like we said don't send

transactions now let's go ahead and

actually send a transaction let's update

the blockchain let's update our contract

by storing a new favorite number so

let's do 7878

and we'll hit store and we'll press this

orange button you'll see you'll get

prompted with metamask actually popping

up saying okay let's update the

blockchain let's send this transaction

and if we go ahead and hit confirm the

exact same thing happens we'll get this

transact to simple Storage storage

transact to simple storage. store

pending view an ether scan this little

check mark we view it we can see the

transaction indexing on ether scan and

after you wait for a little bit the

transaction will go through and now if

we hit the retrieve button we can see we

have now stored 7878 on chain if we copy

the contract address again we paste it

into sapoia ether scan we scroll down

after a few minutes we'll actually see a

second transaction come through we see

two transactions associated with this

contract the first transaction obviously

is the contract creation transaction and

the second transaction is us actually

calling the store method ether scan is

smart enough to know that this is the

store method it's not always smart

enough to know that but for this one

it's smart enough to know and we see

that we actually updated our contract

and remember in the future please use

these testet sparingly we're just

starting out and we're just learning so

it's okay for us to send these

transactions here though but let's go

ahead and let's keep going because named

a favorite number of Pat still returns

nothing list of people zero still

returns nothing so let's go to add

person we'll do Pat 16 we'll hit add

person metam Mass pops up obviously

because we're updating the state of our

contract we'll hit confirm we see

transact to simple storage. adderson is

pending it looks like it has succeeded

so now if we do name the favorite number

of Pat we see 16 get returned and if we

do list of people at zero we see we get

Pat whose favorite number is 16 and

guess what at this point you've

successfully deployed a smart contract

to a real test net congratulations you

should be incredibly excited for

yourself be sure to give yourself a pat

on the back maybe go for a walk maybe

have an extra cup of coffee or an ice

cream because additionally you've also

interacted with that contract with these

buttons and remix that allow us to send

transactions to update the state of our

contracts congratulations you're a

solidity developer but we've got a lot

more to go and like I said make sure to

celebrate these little wins celebrating

little wins will motivate you and excite

you to continue to move forward so be

sure to take the time to Pat yourself in

the back congratulations if you've got

this far there's a ton more for us to

learn but just you getting here is a

fantastic achievement in itself now here

if we wanted to deploy to a different

test net all we would have to do in our

metamask is switch to a different testet

like linear Gilli since we don't have

any linear Gil we actually can't deploy

this to a test net but if we used a

faucet to get more linear gorill eth

that's how we would deploy it

additionally we could do the same

methodology for deploying to ethereum

main net or any other main net that you

want to work with throughout this course

the difference here is obviously you

just need to buy some ethereum to

actually deploy this smart smart

contract remix will automatically update

to whatever Network you're working with

for example right here it says Ah you're

working on the main network but if we

were to switch to gelli it would say ah

you're working on gelli but if we were

to switch again it would say ah you're

working on lenia in the future we'll

learn to add different networks so you

can learn how to deploy to any other evm

compatible network that you want

to now I've mentioned this a couple of

times but whenever we compile this code

it compiles it down to something called

the evm or the ethereum virtual machine

don't worry too much about exactly what

this means but essentially the evm is a

standard for how to compile and how to

deploy smart contracts to a blockchain

any blockchain that is evm compatible

you should be able to deploy solidity

code to some examples of evm compatible

blockchains and layer 2os which again

we're going to go over working with

layer twos more in the future are going

to be ethereum polygon arbitrum

optimism ZK sync and more just note that

it's important to double check the

blockchain before you launch to it for

example ZK sync is zvm compatible but a

couple of keywords don't actually work

with ZK sync now let's do a quick recap

of everything we learned in this lesson

and then after we do this be absolutely

be certain to take a break maybe go get

some ice cream go get that extra coffee

or whatever you like to do the first

thing you want to do in any smart

contract or solidity code that you write

be sure to write the version that you

want to work with and above the the

version be sure to add the spdx license

identifier if you're not sure what

version to use for now just default to

MIT then you have to create your

contract object and name your contract a

contract is similar to a class in other

programming languages anything inside of

the curly brackets for the contract is

part of that contract there are many

different types in solidity like U 256

string Boolean int Etc if we want to

create our own type in solidity we can

use what's called a struct you can

create arrays or lists in solidity you

can create mappings or dictionaries or

hash tables in solidity where if you

give it a key it'll spit out the

variable associated with that specific

key we can create functions in solidity

that modify the state of the blockchain

we can also create functions in solidity

that don't modify the state of the

blockchain view and pure functions don't

modify the state of the blockchain we

can also specify different data

locations in our parameters of our

functions but we can only do for special

types like strings strs and arrays call

data and memory mean that that variable

is only temporary and will only exists

for the duration of the function call

Storage variables are permanent and stay

in the contract forever function

parameters can't be storage variables

since they're only going to exist for

the duration of the function call

whenever we hit compile in our smart

contracts it actually compiles our

solidity code down to evm compatible B

code or machine readable code we'll

learn more about those specifications

later

and last but not least congratulations

on your first contract

here all right let's get started now

with our lesson three remember

everything is in the GitHub repository

or the web3 dev. education we scroll

down once again we can scroll to lesson

three and again a lot of this is undone

but it'll be done for the actual video

scroll down to lesson 3 and we have

lesson 3 remix storage Factory all the

code that we're going to be working with

is in this remix storage Factory f23

GitHub repository all of the GitHub

repos associated with this course end

with

f23 which stands for Foundry 2023 I'm

going to first do a brief walkthrough of

what we're going to be coding for this

lesson so for now just sit back and

relax and enjoy for this lesson we're

going to be working with three new

contracts our original simple storage

doso which we're going to do a slate

modification to a new five storage. or

add F storage. and a storage factory.

soou our storage factory. is actually

going to be responsible for deploying

new simple storage contracts yes other

contracts can deploy contracts not only

is this going to be able to deploy other

contracts but but it's going to be able

to interact with other contracts as well

what we could do is we could deploy this

to a remix VM H deploy we'll compile all

of our code go to a remix VM scroll down

to select the contract we're going to

select storage Factory not simple

storage deploy this see that contract

that we just deployed down at the bottom

and you'll see our top function is this

function called create simple storage

contract where if we pull up our

terminal and we click create simple

storage contct contract you'll see we

get a new transaction at the bottom and

this transaction is the transaction that

we deployed a simple storage contract

from our storage Factory contract now we

can actually go ahead and interact with

our simple storage contract remember in

simple storage we have a function called

store which takes a favorite number we

can actually call this store function on

our simple storage contract from our

storage Factory contract using this F

store function so we'll add the index of

our simple store contract which since we

only deployed one so far it'll be at

inex zero and we'll say our new favorite

number is 1 123 and we'll hit F store

and we'll click SF store at 0123 SF

store stands for storage Factory Store

so we're going to store the number 123

on index0 and again don't worry about

this making too much sense yet we're

going to explain this all in a minute

now if we hit SF get of zero we'll go

ahead and get back 1 2 3 we're saying

let's get the value of the simple

storage contract stored at index Zer and

we do indeed get 1 2 3 additionally we

have this list of simple storage

contracts array or list and it's only

size one right now but if we type in

zero here we get back the address of

that original simple storage contract

that we deployed additionally in this

lesson we're going to learn about a ton

of incredibly important solidity

features such as Imports and inheritance

without further Ado let's get

froggy and one more time of course

remember all the code is available in

The Foundry full course f23 of the chain

exelor or on the web 3d. ucation site

once it's up so here we are back in

remix with our simpl storage. soulle if

you skipped over the last section and

want to get that contract just come to

the full repository go down to lesson

two go over to the code in the GitHub

repo associated with this course the

remix simple storage f23 and just copy

and paste everything into remix yourself

to make sure you've done it correctly be

sure to hit compile we have our simple

storage contract that we created in our

last lesson which is great it allows us

to store our favorite number and it

allows us to store a list of people who

have different favorite numbers also a

mapping and some other different

functionality with interacting with

people's favorite number but we want to

go even further with this we want

another contract to actually deploy this

simple storage contract for us and

interact with it contracts interacting

with each other seamlessly and

permissionless is a feature of smart

contracts and blockchain development

that's absolutely essential and crucial

and one of the reasons why blockchain

development is so powerful the ability

for contracts to interact with each

other seamlessly is something known as

composability smart contracts are

composable because they can easily

interact with each other this becomes

even more important when we get to

topics such as defi where we can have

incredibly complicated Financial

products and instruments interact with

each other seamlessly because they're

all using the same smart contract

interface so we're going to keep our

simpl storage. the exact same way it was

from the last lesson and we'll update it

in a little bit but let's go ahead and

create a new contract called called

storage factory. Soul so let's go ahead

and get this contract set up now we're

going to be doing this a lot and when we

work with AI pair programmer now we're

going to be doing this a lot and when we

work with AI pair programming this is

going to be a lot easier for us to do

but for now repetition is the mother

skill so let's keep going first thing we

need to do is what if you want to pause

the video and add the first two things

you should put at the top of every slity

smart contract right now go ahead but

for those of you who didn't pause let's

go ahead and do

spdx license ident to fire MIT and then

let's do pragma solidity

0.818 or 19 or whatever you want to do

you know what let's do 19 what do we do

in simple storage we did 18 let's do

18 and then we'll do contract so this

will be the third thing actually

contract storage Factory like this and I

hit command s but you can also go and

compile like so and I'm also just going

to add the carrot here meaning we're

going to use 0.818 but any version

greater than that all also works as well

awesome now this storage Factory

contract is going to be deploying a

simple storage contract so let's create

a function that can actually deploy or

create a simple storage contract so

we'll say function create simple storage

contract and we'll make this a public

function and we're going to have this

create simple storage contract function

deploy a contract and then save it to a

state variable or a storage variable but

the question is okay well how does the

storage Factory know what the simple

storage contract even looks like how

does this contract know about this

contract how does this contract know

that this contract even exists the first

way that we could do this is we can

actually go to our simple storage. Soul

contract and start highlighting from the

contract word and scroll all the way

down to the end of the contract copy it

command C or rightclick copy go back

over to storage Factory and Below pragma

solidity but above contract storage

Factory paste it in here if we go ahead

and command s or compile this you'll see

that this actually goes ahead and

compiles successfully huh so this is to

show you that yes right now in our

storage factory. soulle we have contract

simple storage which ends here and we

also have contract storage Factory down

here you're allowed to have multiple

contracts in the same file now this

isn't a best practice because we really

don't want to be having multiple

contracts in the same file when we could

separate them out into their own files

as your projects get bigger and bigger

if you just add all of your contracts

into the same file it can get really

really confusing really difficult to

jump around the code and find the places

where you want to add stuff so normally

it's best practice to keep them

separated like we did above but we'll

learn a little bit more about how to

keep them separate in just a minute if

you go down to the deploy Tab and you

say on the remix VM and scroll down you

actually have this section to choose

your contract we can choose either one

of these contracts right now and if on

the right side you have storagea

factory. in this contract section you

can actually choose either one simple

storage or storage Factory and you can

see they're both in storage factory.

soulle if on the right hand side we go

to simple storage and we go back to this

contract section we can only chose

simple storage because the simple

storage contract only has one contract

in it the storage Factory has both

simple storage and storage Factory so

that can get a little confusing as well

if you have multiple contracts in the

same file but let's stick with this

methodology for now in our storage

Factory and let's even close out simple

storage. Soul at the top just so we

don't get confused in our storage

factory. Soul let's scroll back down to

storage Factory because now that we have

our simple storage in this file we can

actually deploy the simple storage

contract so this function is going to

deploy a simple storage contract but

we're going to save it to a storage or

state variable and we're going to do it

the exact same way we've been saving any

variable first thing remember like

remember how we did U 256 public

favorite number this was in the format

type visibility name we're going to do

the exact same thing the type of a

simple storage contract is going to be

simple storage and the reason that

solidity is going to be able to identify

this keyword is because it's the same

name as contract in the same sense that

our struct keyword allows us to create a

person type the contract keyword allows

you to create a new type of well a type

of simple storage contract so simple

storage for now we'll just give it a

visibility of public and we'll give it a

variable name simple storage now this is

going to be a syntax you're going to see

a lot and it might be a little bit

confusing the first couple times you

read it the difference between these two

is very subtle the difference between

simple storage on the left and simple

storage on the right is very subtle it's

simply that the S is lowercased over

here and the S is capitalized over here

solidity is case sensitive so these are

actually different word simple storage

here is referring to the contract simple

storage here is referring to the

variable you'll often see people use the

syntax when working with contracts where

they name the variable the exact same as

the contract itself if this is confusing

to you you can do my simple storage

instead of simple storage with lowercase

so either one of these works it's good

to get used to this as such but if

that's confusing you can do my simple

storage now in our create simple storage

contract function we're going to say

simple storage equals new simple storage

like this this new keyword is how

solidity knows to deploy a contract so

adjust this code alone if we go to the

compile tab we compile this this does

indeed compile we can go to deploy we

need to make sure we're on the storage

factory. Soul on the right hand side

we'll scroll down to the contract we can

actually deploy our storage Factory like

so hitting the deploy button and

remember you can see the transaction in

the terminal here and we can scroll down

to the contract right now there's two

buttons we have our blue view function

simple storage because again the public

keyword automatically gives the variable

name a getter function or a view

function and of course we have our

create simple storage contract orange

button because it is actually a

transaction right now simple storage

returns nothing the zero the default

value for an address which is the zero

address and if we call create simple

storage contract we get see a green

check mark meaning that transaction went

through now if we call the simple

storeage blue view function we see we

indeed get an address here we have

deployed our simple storage contract

from another contract oh my goodness so

congratulations now you know how a

contract can deploy another contract

awesome

job but the thing is like I was saying

if we just add all of our contracts into

the same file and we have these massive

contracts all interweave between each

other and can get very cluttered and

very confusing so is there a better way

we can actually arrange and organize our

code other than this and this is

actually even a little bit redundant

since we already have our simple

storage. soulle if I change something in

here then I would also have to go and

change it in here and that's too much

work for me as an engineer I will work

incredibly hard to be incredibly lazy so

instead of doing this we can use what's

called an import if we go ahead and

delete our contract simple storage in

our storage Factory here so that now we

just have the storage Factory contract

we can go ahead and use the import key

word to import simple storage. soulle so

we can do

import

do/ simple

storage. and a little semicolon here

this import do/ simple storage. is the

exact same as if we had this giant

simple storage in here so this import

simple storage. soulle is a shorthand

version of copy pasting that simple

storage. soulle into this contract and

now we're able to have simple storage.

in its own file and storage Factory just

import it from simple storage making our

lives much easier it takes our path

package or GitHub which we'll explain in

a little bit and and copy paste whatever

in that file at the top of our file

literally solidity for us is copy

pasting everything in here and sticking

it up here so we can go ahead run this

again let's compile delete our old

contract run remix VM let's be sure

we're on storage Factory we'll go to

storage Factory we'll deploy it scroll

scroll down click here simple storage

starts up as nothing create simple

storage oh my goodness look we deployed

a contract huzzah great work so now that

we're starting to work with different

files there's a number of things we want

to consider first one is actually the

solidity version so right now we're

using 0.8.1 with no carat and in storage

Factor we're using 0.8.1 with a carat if

I were to for example move the solidity

version of this down to

0.8.6 and go to compile this with a

different version remix is actually

going to remix is actually going to

automatically bump this up to

0.8.9 or actually remix is actually

going to automatically bump this up to

0.818 if I'm on the simple storage

because 0.818 is the version that works

for simple storage and it still is

compatible with storage Factory however

if I were to take storage Factory and

move it to

0.7.5 and try to compile it's going to

try to compile this with

0.7.0 and our simple storage with 0 .

7.6 and it's not going to be able to do

it for both and so we're going to get a

compilation error so when working with

multiple files it's important to keep

the version of solidity in mind because

you want to make sure that all of your

contracts can actually compile together

so this is great and all but right from

the get-go I want to teach you the more

advanced import that you should always

use so this is good but we actually

never want to default to this we want to

default to something called named

Imports let's say our simple storage.

Soul contract had a ton of other

contracts like contract simple storage 2

simple storage 3 simple storage 4 and

these were all massive massive contracts

as we have this right now import simple

storage. would import everything from

here simple storage simple storage 2

simple storage 3 simple storage 4 and if

these files were incredibly big when we

deploy our storage Factory it would have

to calculate all this extra computation

making the deployment of our storage

Factory more expensive if that's

confusing to you don't worry about it

right now additionally in the future

these can import from weird places that

aren't compatible with storage Factory

again that's not going to make sense

quite yet and that's okay but in any

case there's a way for us to not import

this whole file but only a very specific

contract or a specific section of our

simple storage. sole so instead what we

can do is in our import statement we can

specify the exact contract that we want

to import from this file so in our

simple storage. soou let's say we do

have these other contracts in here we

could say we only want to import simple

storage not simple storage 2 not not

simple storage 3 not simple storage 4 by

saying import these little brackets here

simple storage from simpl storage.

soulle and this goes ahead and compiles

correctly we could also import multiple

contracts from our simple storage for

example we could do import simple

storage simple storage 2 from simple

storage. soulle this way we only import

the exact specific contracts that we

want from these other files and I

promise you in the future always

referring to named Imports instead of

this type of imports will save you a lot

of headache in the future so always

default to this never default to this

just by learning this you are already

better than 80% of the current solidity

developers so

congratulations but all right fantastic

so we've learned about Imports we're

able to import our simple storage from

simpl storage. soou We're importing it

in the more advanced way

congratulations now already here you

might actually start running into some

questions right and we're going to get

more and more advanced with this course

and you're going to have questions which

is a good thing if you don't understand

stuff that means you're thinking

critically and you're approaching the

subject matter the right way so this is

where we're going to jump into again

doing a little bit of an AI chat example

so for example on this line let's say

you're a little bit confused and you go

what's the difference between simple

storage here and simple storage here I

don't understand so let's learn how to

work with chat chbt or any AI buddy to

ask them to help clarify so we're going

to go ahead I'm going to hit command a

or you can just highlight everything

command C to copy or rightclick copy

we'll go over to chat gbt and in here

we're going to ask the question hi I'm

having a hard time and let's zoom in

understanding the difference between the

simple storages on this line and here's

where we want to be very specific when

we're talking with AIS so I'm going to

hit shift enter so that it doesn't

actually send the question to chat TBT

but I'm going to put three back ticks

shift enter again and actually I said

we're going to copy the whole thing but

let's just copy this this single line

and paste it in here shift enter again

three back ticks again adding this

delimiter tells chat gbt that this is a

block of code and it makes it easier for

chat gbt to be able to understand that

this is a block of code and I'll hit

shift enter twice and if you have a lot

of code you're not going to be able to

copy your whole contract because a lot

of these AIS can only understand so much

in a question but this is small enough

that we can actually just go ahead and

copy the whole thing bring it back over

to chat yout and say here is my full

code and then we'll do again shift enter

three back ticks shift enter paste shift

enter three back ticks so now we have a

little AI prompt here that we can ask in

chubbt and and I don't have this in here

yet but in the GitHub repo associated

with this lesson I will add this AI

prompt in here so let's go to the bottom

and I was saying you need to use shift

enter but I guess you could just use

enter that's fine let's go ahead and

click the send button and it'll send

send it the question so now it'll start

outputting here and let's see what it

says and this is where we can already

start to see the power of these AI

buddies as learning buddies we see in

the given code simple storage is a

variable of type simple storage which is

a contract defined in simple storage.

Soul tells us what the line is doing it

clarifies the differences a little bit

more and a lot of this beginner basic

stuff AIS are really good at once we get

more and more advanced AIS are going to

start breaking apart but but at least

for the beginning of this course AIS are

going to be incredibly helpful and

Incredibly good at explaining a lot of

these what we could do if we wanted to

is we could also go ahead and copy this

prompt we can go over to something like

Bard paste it in here and ask Bard the

same thing and here's already a good

example of where an AI can get things

wrong if we scroll down it's telling me

you can use simple storage variable to

interact with the new simple storage

contract for example you could call the

set function to set the value on stored

data variable or you could call the get

function to get the value of the stored

date variable uh there is no stored data

variable so I don't know where it's

getting that from so just remember keep

in mind that AI can get things wrong and

that when they do there are other forums

that to use as well like I said we're

going to be learning about them as we go

on like stack exchange of theum piranha

or like I said of course the discussions

for of this course so if Bard or chbt or

whatever AI budy you're working with

gives you something confusing be sure to

go to the GitHub discussions or ask on

one of these

forms now as you can see though right

now every single time we call create

simple storage contract we're going to

deploy a new simple storage contract but

we're going to override it in this

simple storage right so if we go ahead

and deploy this right now scroll down

here simple storage at the zero address

create okay now it's at a new address

create again okay now it's at a new

address we're not keeping track of all

the different addresses that this simple

storage contract is being deployed to so

let's actually create a running list of

all the different simple storage

contracts that we're deploying so

instead of having this variable be just

a single simple storage contract let's

have it be an array or list of simple

storage contracts and we'll change the

name to list of simple storage contracts

so now when we deploy it instead of

saving it like this we're going to do

what we did before in our last section

we'll say simple storage new simple

storage contract equals new simple

storage and then we'll push it onto our

Dynamic array so we'll say list of

simple storage contracts push new simple

storage contract so let's go ahead and

compile this okay looks good let's go

ahead and deploy this we'll delete our

old one we're on the remix VM great

storage Factory and look at this you can

even see make sure we're on storage

Factory okay great we'll go ahead and

deploy that awesome we get list of of

simple storage contracts which now has

this U 256 input which allows us to

choose the index of the variable we'll

go ahead and create simple storage now

we go check the zerith index we have an

address if we check the first index

nothing happens if we call create again

which sorry if I have the terminal up

I'll call create again again now there

is one at the first index and since I

called it twice there's also one at the

second there's nothing at the third I'll

hit create again there's no one at the

fourth oh at the third excuse me awesome

so now we actually have a running list

of all of our simple storage contracts

now let's learn how to actually interact

with other contracts from a contract for

now we can think of our storage Factory

as a sort of manager for all these other

contracts so let's learn how our storage

Factory contract can actually call the

store function of the simple storage

that it deploys so let's create a

function called SF store which is going

to stand for storage Factory Store and

it's going to take two variables a u 256

undor simple storage index and a u 256

uncore new simple storage number we make

this public like this now in order to

interact with a contract you're always

going to need two things and we're going

to refer to this a lot you're going to

need an address and you're going to need

the AI now this is technically a lie you

really just need the function selector

but we're going to learn that way way

later in the course for now just think

okay I always need the address and I

always need the ABI the ABI stands for

application binary interface the ABI

will tell our code exactly how it can

interact with another contract we'll go

deeper into the ABI later on in this

course but for now if you go to the

compile tab H compile and you scroll

down there's this little button at the

bottom that says copy abi2 clipboard or

you can also go to compilation details

you can see a ton of information about

the compliation details such as the bite

code with the op codes some metadata the

name but also the ABI which tells us the

ways we can interact with this contract

if we hit the drop down for the zero we

see there's an input create simple

storage contract which is one of our

functions and you see state mutability

which we'll talk about later but if we

had another drop down we see list of

simple storage contracts and the other

drop down we'll see SF store these as

you know are the buttons that we can

press when we deploy this contract right

so if I redeploy this we see those exact

three buttons these are the three

buttons that were inside of that ABI

this is how remix knows to put three

buttons here because it looks at the ABI

and sees that there's three buttons so

in our code here our compiler knows what

the ABI is so in our code here the

compiler automatically knows what the

ABI is because the compiler is the one

that generates the API and we know where

the address is because we have a list of

all of our addresses that we're keeping

track of up here so the reason we have

the ABI is because we're importing our

simple storage contract and actually

let's delete this simple storage 2 we

don't really need the simple storage 2

so when we compile simple storage we

automatically get the ABI for solidity

in the future we'll learn other ways to

get the API so down here let's get a

simple storage contract to interact with

from our list and to do that we'll say

simple storage my simple storage equals

list of simple storage contracts at

index simple storage index like this

since this is an array of simple storage

contracts we can just automatically get

the contract itself like this however

let's say that instead of this being an

array of simple storage contracts this

was an array an array of addresses a

list of simple storage addresses like

this you don't have to code along with

me for this section just go ahead and

follow along and watch if we had a list

of addresses and this would be to be a

little bit different but we had a list

of addresses instead we could say simple

storage my simple storage equals list of

simple storage addresses at the index

and then do something called type

casting and we'd wrap this in

parentheses like so let me zoom out a

little bit so this is something we'll

learn about a little bit later so

basically what we're doing is this list

of simple storage addresses simple

storage Index this line returns an

address and we're wrapping that address

in simple storage like so if this is a

little confusing for you now don't worry

too much about it we will learn about

about it more later now that we have our

simple storage contract we can actually

call the store function directly on this

contract so now we can say my simple

storage. store and we'll add the new

simple storage number and this is great

if we were to deploy this contract right

now though and call this SF store

function though we wouldn't be able to

read the new variable that we just

updated our simple storage contract with

so let's create a function that allows

us to read from our simple storage

contracts as well so we'll create a

function called SF get which will take a

un 256 undor simple storage index is an

input parameter we'll make this a public

view function that will return a uent

256 you in 256 and we'll say simple

storage my simple storage equals and

we'll use this exact same syntax that we

used above to get the simple storage

index equals list of simple storage

contracts at the simple storage index

and now we're going to do return my

simple storage and again if you see

these autocompletes that come up you can

just hit tab but do retrieve so perfect

now let's go ahead and compile we'll go

ahead and delete the old

deploy we'll make sure we're on storagea

factory. soul we'll hit deploy and we

see storage Factory down here now let's

go ahead run through that exact same

exercise so we'll pull up the terminal

just to see our transactions go through

we'll hit create simple storage let's

see that it's actually there at the

zeroth index okay cool we see an address

there so now let's store a new variable

at index0 so at this address so we'll

say at index0 we'll store the number 1 2

3 and actually before I hit this button

if we go down here we hit zero we get

nothing back right but now if I hit SF

store with index zero favorite number 1

2 3 looks like the transaction did go

through now if I hit SF get we go ahead

and get 1 2 3

so our storage Factory contract was able

to create its own simple storage

contract store a variable in that

contract from the storage Factory and we

were able to read back the number one

two 3 all from within our storage

Factory contract feel free to pause

right now and play around with adding

different values creating different

simple storage contracts so that you

really understand what's going on you

can also feel free to hit the little

dropdowns and read more information

about these transactions just as a recap

in our storage Factory contract we have

a function called create simple storage

contract which creates new simple

storage contracts from the storage

Factory contract the reason it's able to

do this is because we're importing from

our simpl storage. file using something

called named Imports we're only

importing simple storage we're not

importing anything in these other

contracts then we use SF store to store

a new number on one of those simple

storage contracts using the index in our

array it can do this because we have the

address address and the ABI the list of

simple storage contracts automatically

compact with the address and the ABI and

then finally we can read back those

simple storage values that we stored now

we can make this sfg function even more

condensed since this list of simple

storage contracts simple storage index

returns an object of type simple storage

we can actually delete this whole line

copy

this paste it here and delete this line

and this will work exactly the same as

what we had before go ahead and save or

compile you'll go ahead and get that

green check mark there this retrieve is

saying we're going to call the retrieve

function on whatever this is and this

whatever this is is of type simple

storage contract we can actually do the

same thing up here by deleting this part

copying this line except for the

semicolon and pasting it over the myle

storage and hitting save or compile

awesome great job so far

awesome now let's say you really like

this simple storage contract you love

all the functionality except for one

thing you wish that the store function

didn't just store the favorite number

you wish it added five so for some

reason you want a contract that does

everything this contract does but just

adds five whenever you call store for

some reason you want everyone's favorite

number to be five larger than what they

think it is well one thing we could do

is we could just copy paste this into a

new file but again that's kind of too

much work for me I'm a lazy engineer

here but let's go ahead and see how we

can approach this problem so let's

create a new file and we'll call it add

five storage. soul and same thing since

this is a new contract we're going to

follow the exact same tips we're going

to do spdx license identifier MIT we're

going do pragma solidity

0.818 let's even do the little carrot

here and we'll do contract add five

storage like so compile great looking

good oh I'm getting a warning

spdx license spelled license wrong so

let's spell that right okay cool looks

good so like I said the first thing that

we could do is we could copy paste

everything in here and then just change

the pieces that we don't like in our ad

five storage this is a little bit

redundant a little bit too much work and

we are Engineers we want to work as hard

as possible to be as lazy as possible so

how can we do that well this is where we

can do something called inheritance we

can have our ad five storage contract be

something called a child contract of our

simple storage contract

and we can have our ad five storage

inherit all of the functionality all of

the functionality of our simple storage

contract so first of course in order for

our ad five storage to know about our

symol storage contract we're going to go

ahead and have to import it so we're

going to do import and we're going to do

once again the named Imports because

we're Advanced solidity Engineers so

we're going to say import simple storage

just the simple storage contract

froms simple storage. soul now if this

do slash is confusing to you don't worry

we'll learn about directory structures

later on in the course and then we'll

say our contract add five storage is

simple storage now our ad five storage

is going to do what's called inherit

everything from simple storage and our

ad five storage is going to have all the

same functionality as simple storage we

can actually see this directly if we go

to compile let's go ahead and delete our

previously deployed contracts we're on

the remix VM let's make sure we're we've

selected ad five storage adiv storage.

Soul let's go ahead and deploy it and if

we scroll down we can actually see oh my

goodness it's got all the same buttons

as simple storage even though the

contract itself doesn't have anything

defined that's because we inherited all

of the buttons We inherited all of the

functionality of simple storage into ad

five storage if you want a contract to

inherit the functionality of another

contract you just import it in and then

say your contract is that other contract

now we can keep going though and add our

own custom functionality into ad five

storage that's not in simple storage so

for example we could say function say

hello it's going to be a public and it

returns a string memory and again you

need the memory keyword because strings

are special in solidity and we can just

say return hello like so this will be a

public pure it's not a view because

we're not reading from storage and again

if that dissertion is a little confusing

to you don't worry too much about it now

but if we go to deploy it it's still

delete our old one we'll deploy this one

we see we have all the functionality of

simple storage plus this say hello

function great but let's delete that for

now let's say instead of wanting to add

additional customization you actually

love every function in here except for

one remember the reason we wanted this

adiv storage. soulle is because we

actually want to change the store

function to have it add an additional

five to people's favorite numbers maybe

you're mischievous and you want people's

favorite numbers to be five greater than

they are well to add this ad five

customization to that store function we

can do something called overrides to do

overrides there are two keywords that we

need to be aware of those are virtual

and override if our were to try to

create a store function for our ad five

storage right now what do you think will

happen well let's try it out so let's

say function store un

256 undor new

number public if we try to compile this

right now we'll actually get an error

even if there's nothing in this store

function we roll over we say from

solidity type error overriding function

is missing override specifier and

remember if you get lost or confused an

error like this is something perfect for

you to ask chat TBT or maybe even find

we could say I am trying to compile my

solidity code but I'm getting this error

we can copy this whole error here paste

it in here and then in additional

context we'll just add the code like

this we'll hit search see what it gives

us we'll say and it looks like find was

able to find the answer the error

message indicates the function store in

the ad five storage contract is missing

the override specifier which is required

because it overrides a virtual function

from the simple storage contract thanks

I'll explain what find is giving us in

just a minute it's right we need to tell

solidity that it needs to override the

store function in simple storage we want

to be very explicit and say hey do this

store function and not what's in simple

storage. soole so let's go ahead and add

that keyword override now though if we

just add that keyword we go ahead and

try to compile we still get an error

trying to override a non- virtual

function did you forget to add virtual

in order for a function to be override a

bowl you need to add this virtual

keyword in the base class or the parent

class so in simple storage we need to

add virtual to store this virtual

keyword means that this function is

overridable any function that doesn't

have this keyword you can't override now

our store function is override a and

we've specified that we are indeed going

to override the store function now if we

go ahead and compile we'll see

everything compiles successfully all

right great so now let's just add the

functionality to store remember since ad

five storage inherits everything from

simple storage this means that we even

have access to my favorite number so

what we can do is we can say my favorite

number equals underscore new

number plus 5 we'll compile this and now

let's try it out we're on remix VM we

want to make sure we're with ad five

storage we'll delete the other ones

we'll deploy scroll down hit the drop

down retrieve currently return zero now

if we store two pull up the terminal to

make sure we're actually sending

transactions we'll hit store and now if

we hit retrieve we see we indeed get

seven back cuz 2 + 5 is 7 we add five we

hit store retrieve now returns 10 So

This Is How We Do inheritance and

override

functions and that's it for this section

you've learned a ton of incredibly

powerful features in solidity so let's

do a quick recap of what we learned this

section we learned that with the new

keyword we can actually deploy contracts

from other contracts we learned that we

can actually import other contracts

which is essentially the same as copy

pasting the code into this file we also

learned this thing called named Imports

which is going to make you look even

better than most of the solidity devs

out there we learned that we can

interact with other contracts so long as

we have the address and the ABI the

simple storage type automatically comes

with the address and the ABI so we can

just access it like this we didn't learn

too much about the ABI but we'll learn

more about it later we learned that if

we want to make a child contract and

inherit the functionality of some other

contract we can just import that

contract and then use the is keyword in

the contract declaration to override a

function we need the override keyword

and we need the base class or the parent

class to have the virtual keyword on the

function you want to override and that

is the end of this lesson so be sure to

give yourself a huge pat on the back

take a break breaks are good for your

brain go for a walk grab a coffee get

some ice cream go tell your friends go

post on Twitter you're getting more and

more advanced with solidity very quickly

so be sure to celebrate the little wins

to keep being excited and keep that

Curiosity congratulations youve

completed this lesson

all right everybody welcome back we are

now headed into Lesson Four this is

going to be our remix fundme and once

again you can find all the code

associated with this lesson in the

GitHub repository associated with this

course and also web3 dev. and let's do a

quick walkthrough of these contracts

before we actually start coding anything

to see what we're going to be doing

we're going to be creating one contract

funme doou we're also going to have

another file called price converter

dossou and we'll talk about that in a

little bit the fundme contract is going

to be our main contract this is going to

be an example of a crowdsourcing

application or a way to raise money you

can think of it as a web 3 decentralized

Kickstarter will allow users to send

ethereum polygon Avalanche Etc or really

any native blockchain cryptocurrency

into this contract and allow the owner

of the contract to actually withdraw all

the funds for them to go spend on their

new project and we are going to actually

deploy this contract to a test net and

remember use the test net transactions

sparingly but if we deploy this to a

test net we scroll down we actually see

that we have a couple of buttons and a

new color button we'll actually get a

new red button for our fund function a

red button indicates that a function is

payable and we can send native ethereum

or polygon or Avalanche or whatever the

native cryptocurrency of the blockchain

we're working with is We additionally

will indicate a minimum USD amount to

send to the contract so fun have to

spend at least $5 worth of ethereum in

order to call this fund contract so if

we go up to the value section we can

actually send some value with this

transaction and again don't worry about

this making sense yet but if I want to

send 0.01 ether I'll grab that amount in

way paste it into the value section here

I'll scroll down I'll hit the fund

button minimass will pop up I'll confirm

we can see at the top the current

balance of the contract is zero and

we'll wait a little bit for the

transaction to finish going through and

after the transaction finish is going

through we can see ether scan we have a

balance of 0.01 eth and we can also see

that after remix after a slight delay

then we can allow the owner of the

contract to withdraw those funds right

now the owner of the contract is also us

and after this transaction goes through

we'll see that balance removed from the

contract and it'll go back into our

wallet and as you just saw there if we

held our metamask up for long enough

eventually it would pop back into our

metamask are you excited we you should

be because after you complete this

section you'll actually know most of the

fundamentals of working with solidity

we're going to going to be going over a

lot of advanced features in this section

and I'll let you know the specific parts

that you don't need to fully understand

quite yet there's going to be a couple

parts where if it doesn't totally make

sense just keep going with the course

and as we get later into the course

you'll figure out why they make sense

but it might be a good idea to write

down the questions that you have to ask

either an AI on the GitHub discussions

or web3 education. make sure of course

to use the discussions Tab In The

Foundry full course f23 to ask questions

and interact with other developers who

are taking this same course or go to

web3 dev. education to learn more all

right let's get

froggy so the first thing that we want

to do is let's once again delete

everything in our remix so we can start

from scratch so I have the contracts

that we're actually going to be building

in here you might have the simple

storage the ad five extra the storage

Factory Etc let's go ahead right click

and just delete everything we're going

to start completely from blank here so

let's go ahead and delete everything in

here all right great so let's go ahead

and start creating our contract we're

going to call it fund. Soul one thing

that's really good when you actually

start building any code at all is to

First write down what you want it to do

so what do we want ours to do we want to

get funds from users into this contract

withdraw funds to the owner of the

contract or whoever has created this

fundme contract and then we also want to

set a minimum funding value in USD we

don't want people to be able to donate

just a penny so let's go ahead and set

this up

spdx license identifier identifier MIT

do pragma solidity carot

0.818 contract fund me let's go ahead

and delete these comments so before we

embark on writing all of our

functionality out let's just write down

the functions that we want to build so

we're probably going to want a function

fund which is going to be the function

they call to send money to our contract

we're going to want a function withdraw

which is going to be the function that

the owner of the contract is going to

use to withdraw the money that the

funders send us and those are going to

be the two main functions that our

contract is going to need we're going to

be implementing more functions than just

this but these are going to be the main

functions to interact with our protocol

or interact with our fundme contract

let's comment out withdraw for now and

just start focusing on

fund we want anyone to be able to call

this fund function so we're going to

make this public and we want this

function to do what well we wanted to

allow users to send money and we want to

have a minimum dollar amount that they

have to send so the first question we

need to answer is how do we send eth to

this contract how do we have it when a

user calls the Fone function eth

automatically gets sent into our

contract whenever we send a transaction

on the blockchain there's actually

always a value field that gets populated

and most of the time it gets sent with

zero even before when we called the send

function between our accounts when we

added an amount in our metamask this

amount value populated the value field

of our transaction this value field is

the amount of native blockchain

cryptocurrency that gets sent with every

transaction the first thing that we need

to do to allow a function in solidity to

accept this native blockchain currency

in the first place is to make the

function payable it's this payable

keyword that makes the function look red

in the remix UI just like how wallets

can hold funds contracts can actually

hold funds as well so whenever you

deploy a contract similar to a wallet

address it actually acts almost the same

as a wallet address you can send money

to it you can interact with it Etc and

like we did in the demo you'll see this

contract actually gain a balance just

like a wallet you can access this value

amount of a transaction using one of the

globals in solidity called

message. solidity has a number of these

globally available keywords and

functions and you can find these in the

solidity documentation one of them is

message. value which is the number of

way sent with the message if we wanted

users to be required to spend at least

one whole ether with this fund function

we could use something called require to

do so in order to do that we would add

this line require message. value is

greater than 1 E8

and there's a couple of things to unpack

here 1 E18 is equal to 1 ether which is

equal to 1 1 2 3 4 5 6 7 8 9 10 1 2 3 4

5 6 7 8 or put another way it's equal to

1 * 10 raised to the 18th in solidity a

double asri or double multiply sign is

how you do a power or an exponent this

value here is the value in way of one

ethereum in your smart contracts and at

the lowest level this is how they

process numbers in this giant wave

format so if we wanted people to be

forced to send at least one whole eth

with this fund function we would just

say require message. value is greater

than 1 E18 you can use something like

eth converter.com see to convert one

ether between ether whey and gay is

actually another value in between ether

and Wei and we saw gu actually when we

saw gas costs normally gas costs are

shown in forms of guay this required

keyword is a checker it's basically

saying hey is message. value greater

than 1 E18 if not then revert this

transaction and if we want we could add

a little revert message we could say

like didn't send enough eth we can

actually deploy this we can actually

compile and deploy this on a remix

vmy scroll down and if we hit fund and

if we pull up our terminal we hit fund

we actually see we get this little X

here meaning our transaction didn't go

through and if we hit the drop down oh

again same thing same thing we know that

this error is because we have this

require statement in here in our

transaction is reverting or not going

through so we know that with this

transaction we need to send at least 1

eth or or 1 E18 way worth of eth in the

value section of our transaction so if

we scroll up we can actually just change

the unit to Ether put one in here scroll

down and now if we hit fund oh it

doesn't go through because we have

strictly greater than so excuse me Let's

do let's do two now I'll scroll down

we'll hit fund and we see we get a green

check mark and we see the fundme balance

actually has improved to two if we

update the value to two again and we

scroll down we had fund again we see our

transaction went through and we have

four if we try to do less like let's

change this to way and we'll do you know

th way scroll down we hit fund up it

fails because 100 way is less than 1 E18

way right because 18 E18 way is this

much way so obviously th000 or however

much I put in is much less so this

require says if this first section is

false then go ahead and revert with

whatever this second section

is reverts can be a little bit confusing

and a little bit tricky so what is a

revert a revert undoes any actions that

have been done previously and sends the

remaining gas associated with that

transaction back so what does that

actually mean well let's say for example

in our fundme contract we have a u 256

public my value and let's have my value

initialized to one now in our fun

function let's say my value equals my

Value Plus two so every time this fun

function successfully goes through we

add two to my value however if we get to

a revert statement even though we added

two to my value previously since our

contract reverts this would actually

revert this action or reset it back to

its initial state so if this transaction

reverts my value would go back to one or

whatever it was previously if we compile

fundme we delete our previous deploys

we're on the remix VM we'll deploy

fundme we'll scroll down we have my

value which defaults to one if we call

fund right now without any value we pull

up our terminal we can see the

transaction failed my value is still one

even though this line technically

executed this line executed but then

this line hit and it reverted what was

done here so if we scroll back up though

we go to Ether we'll put one in for now

scroll back down now we'll hit fund oh

needs to be more than one excuse me

we'll add two here scroll back down now

we'll hit fund that transaction did go

through which means my value will now be

equal to three and again if I set value

to zero we call fund it reverts so my

value is still three so then the

question might be oh well did we spend

gas to do this if my transaction didn't

even go through well unfortunately the

answer here is yes if you send a failed

transaction you will spend gas because

computers executed this line and then

they executed this line and just failed

so users can actually specify how much

gas they send with every function let's

say there was a ton of computation after

this require line we would need to send

a ton of gas to operate and run our fund

function however once it gets to this

require line and it reverts however much

gas that we sent to execute the rest of

the computation would just get refunded

to whoever initiated the transaction

like I said sometimes the refunds and

some of that can be a little bit

confusing so again for now just know

that if a transaction reverts it undoes

anything it does previously and you can

consider consider the transaction failed

however if you send a reverted

transaction you will still spend gas but

okay let's delete this value for now

delete it from the global scope and

delete some of these like that in fact

every single transaction that we send

will have these fields it'll have a nuns

or the transaction count the account the

gas price the gas limit that we've seen

on ether scan a two aka the address that

the transaction is sent to a value which

is going to be this amount that we're

talking about we'll also have data which

is going to be what we send if we make a

function call or deploy a contract and

then it'll have this vrs components

we're not really going to go over these

VR ands because this is that

cryptographic magic that's happening

when a transaction is signed but just

know that that's in there for sending

value we can populate some of these

fields the gas limit for example is

populated to 21,000 data is going to be

empty and then that two is going to be

the address of the transaction want to

send to for a function call we can also

still populate the way that we want to

send so we can call a function and send

a value at the same time in remix it has

a little drop down here way gu finny and

ether we're going to ignore finny for

now but of course we have our whey gay

and ether again where one ether is worth

this much gay and this much

whey so right now our contract is pretty

minimal right we're requir iring the

message. value is greater than one whole

ether but we want to actually require

that it's less than some value like

let's say we want to have users spend a

minimum of $5 as opposed to one whole

ethereum so let's first specify that $5

we can do that at the top of our

contract we'll say U 256 minimum USD

equals 5 and we'll make this public

instead of internal we'll update this

minimum USD in the future to make this

more gas efficient so what we want to do

is we want to require that our fun

function requires that the message.

value is greater than let's say greater

than or equal to minimum USD however

minimum USD is in terms of USD or

dollars and message. value is in terms

of eth or way in terms of ethereum so

how do we convert the amount of ethereum

to its price in dollar this is where

oracles and chain link comes into play

the dollar price of an asset like

ethereum is something that we've

assigned to ethereum outside of the

blockchain in the real world so in order

to get this abstract concept of the

price of the Native cryptocurrency of

the blockchain working with so we need

to use a decentralized Oracle Network or

something called an oracle to get this

price so before we keep going let's

learn a little bit more about

decentralized oracles chain link and how

they work so that we can understand how

to get the price of ethereum into our

smart contracts as we've talked about

blockchains are deterministic systems

which means that they themselves can't

actually interact with real world data

and events they don't know what the

value of an ethereum is they don't know

what random numbers are they don't know

if it's sunny outside they don't know

the temperature they don't know who's

President they don't know any of this

information these blockchains also can't

do any external computation maybe you

have some amazing artificial

intelligence model that you want to

integrate with a smart contract smart

contracts by themselves can't do

anything with that as we've mentioned

this is because blockchains are

deterministic by Design This is so that

all the nodes can reach consensus if you

start adding variable data or random

data or values that return from an API

call different nodes could get different

results and they would never be able to

reach a consensus this is known as the

smart contract connectivity problem or

the Oracle problem and this is bad news

because we want our smart contracts to

be able to replace traditional

agreements and traditional agreements

need data and they need to interact with

the real world this is where chain link

and blockchain oracles come into place a

blockchain Oracle is going to be any

device that interacts with the offchain

world to provide external data or

computation to Smart contract

however the whole story doesn't even end

there if we use a centralized Oracle we

are reintroducing a point of failure

we've done all this work to make our

logic layer decentralized but if we get

our data through a centralized node or

through a centralized API or we decide

we want to make the API call ourselves

we are reintroducing these trust

assumptions that we've worked so hard to

get rid of we're essentially ruining the

entire purpose of building a smart

contract so we don't want to get our

data or do external computation through

centralized nodes those are bad news

chain link is the solution here chain

link is a decentralized Oracle Network

for bringing data and external

computation into our smart contracts as

we mentioned before this gives rise to

these hybrid smart contracts which

combine onchain and offchain to make

incredibly featur powerful applications

chain link is a modular decentralized

oracal Network that can be customized to

deliver any data or do any external

computation that you like so for example

a lot of people say oh I can just make

an https call to some

API and we'll be good to go the

blockchain nodes can't make these https

calls because they wouldn't be able to

reach consensus if they called the node

at different times or they did something

else all the consensus would be broken

so instead we need a decentralized

network of chain L oracles to do this

and then in transaction this network of

nodes will return the data to our smart

contracts for us now chain link networks

can be completely customized to bring

any data or any external computation

that you want however doing the

customization can be a little bit extra

work there are a ton of chain link

features that come out of the box

completely decentralized ready to Plug

and Play into your smart contract

applications what are those features the

first one is going to be chain link data

feeds and that's the one we're actually

going to be using for our application

here chain link data feeds currently at

the time of recording are powering over

$50 billion in the defi world the way

they work is a a network of train link

nodes gets data from different exchanges

and data providers and brings that data

through a network of decentralized chain

link nodes the chain link nodes use a

median to figure out what the actual

price of the asset is and then deliver

that in a single transaction to what's

called a reference contract a price feed

contract or a data contract on chain

that other smart contracts can use and

then those smart contracts use that that

pricing information to power their defi

application we can see an example we see

an example at data. chain.

link and you can change networks you can

change price feeds you can change whole

bunch of information to see some of the

most popular price feeds let's look at

ethusd for

example on ethusd we can see this whole

network of independent chain link node

operators that are each getting

different answers for the price of vusd

they're getting aggregated by the

network and then delivered on chain we

can see how often they're updated these

ones are updated for 05 deviation

threshold or a few hour heartbeat which

everyone hits first we can see when the

last update was we can see the number of

Oracle responses

Etc we can see the contract address

directly on

chain we can even look at the contract

on ether

scan we can see some of the history we

can see all the responses of the

different

Oracles and then at the bottom we can

see the different users and sponsors

keeping this network

up similar to transaction gas whenever a

node operator delivers data to a Smart

contract the chain link node operators

are paid a little bit of Oracle gas in

the chain link token right now these

users of the protocol are sponsoring

keeping these feeds up and are paying

the Oracle gas associated with

delivering this data on chain here's an

illustration of what the current model

of these data feeds look like a network

of these chain like nodes each reaches

out and gets the information about an

asset and then signs the data with their

own private key in a single transaction

then one node will deliver all the data

with all the different signatures to a

reference contract if that node doesn't

deliver the data another node will send

it instead reputation is incredibly

important when you're a chain link node

operator if you miss data updates if you

forget to send transactions you'll

probably be quickly kicked off these

networks and have no chance of making

any more money in the future these data

feeds are used by some of the largest

protocols in the space such as

synthetics Sushi swap compound and a

with several billion dollars each we can

take a look at an example over at docs.

chain. link work with evm contracts

we're going to hit evm chains scroll

down to data

feeds we'll scroll down to the solidity

section and we can see an example of an

entire contract that uses and reads from

one of these tring price

feeds we can even open this up in remix

and work with it in remix it looks like

this example is reading from a price

feed on coven the reason we're actually

going to use a test net to see this work

is that there's a set of chain link

nodes monitoring the test Network to to

show you exactly how this works out once

we get deeper into the course we'll show

you how to actually run tests and work

with Chain Lake nodes without actually

being on a test net which will make your

development much faster but I highly

recommend walking through this section

along with me so that you can see

firsthand how this actually works so

let's go ahead faucets. chain. linken

we're going to switch to the coven

Network and we're going to get some Coen

eth but remember look at the network

flag and use whatever network is in the

documentation so to get some Coen we're

going to come to the faucet we're going

to turn off test link we'll just stay

with eth I'm not a robot

and then send request once our Coen

ethereum has reached our wallet we can

go ahead and close and we can take a

look in our wallet and see that we do

indeed have 0.1 eth on koven now let's

go back to our remix we'll compile this

contract we go and deploy this on

injected web 3 and again the reason

we're going to use injected web 3

instead of JavaScript VM is that there's

no network of chain link nodes watching

our little fake JavaScript VM there are

network of Chain Lake nodes watching the

test St so we'll scroll down we'll

switch contract to the price consumer V3

and we'll hit deploy mamas will pop up

and after a brief delay we can see our

price feed consumer down here and we can

hit get the latest price which shows us

the latest price of ethereum in terms of

USD you may be wondering why the number

looks so weird that seems like a really

large number for the price of ethereum

in terms of USD and this is because

decimals don't actually work so well in

solidity and we'll get to that in a

little bit there's a decimals flag

associated with this price feed address

that tells us how many decimals to

include with this price it's also in the

documentation however I know that this

one has eight decimals so this is saying

the value of ethereum right now is

[Music]

$3,262 it may of course be different

when you go go ahead and try this now

there's a number of things that happen

in this contract that I'll explain in

our fundme example but if you want to

take a look now and see if you can

figure out what's going on I recommend

you do so price feeds are one of the

most powerful out of the-box

decentralized features you can use in

your smart contract to level them up

especially for decentralized finance if

you're looking for different addresses

of different price feeds you can check

the contract addresses section of the

documentation choose the network that

you

want and then scroll down and then look

some of the different addresses of the

different price feeds for example this

address will give you the price of 1 in

token in terms of ethereum this address

will give you the price of the Apple

stock in terms of USD and so on and so

forth the next decentralized application

right at the box is going to be chain

link vrf or chain link verifiable

Randomness function once we do our

Lottery example a little bit later we'll

talk about how Randomness can be

manipulated in blockchain blockchains

are deterministic system which by

definition means that they can't have

Randomness if you can determine what a

random number is it's not really random

anymore is it so we need a way to get a

provably random number by looking

outside of the blockchain and oracles

are perfectly positioned to do exactly

that chain link verifiable Randomness

function is a way to get provably a

random number into our smart contract to

guarantee fairness and guarantee

randomness of applications many

protocols like pull together axi

Infinity ether cards avag gois and more

chain link vrf for lotteries randomizing

nfts for gaming and for more we're going

to do an example of chain link vrf in a

later section once we get to the lottery

section if you want to see if you can

play with the randomness yourself right

now I recommend you're going to docs.

chain. link evm chains and scroll down

to get a random number and this will

teach you how to get a provably random

number into your applications the next

decentralized out ofth the box feature

of chain link is chain link Keepers

which is decentralized event driven

execution as you've seen in order to

kick off some type of transaction

somebody needs to spend the gas and

somebody needs to sit down and hit the

go button or hit the transact button or

hit the send button this is obviously a

centralized Vector if you have a

decentralized application that needs to

run at specific times or after specific

events are triggered chain link keepers

are the solution to this chain link

keepers are chain link nodes that listen

to a registration contract for different

events that you specify to fire maybe

you say every 10 minutes you want to do

something or once a week do something or

if the price of some asset hits some

number or maybe a liquidity pool is at a

certain level whatever event that you

want to code you absolutely can the

chain link nodes constantly listen for

these triggers to happen and check the

different contracts for these triggers

once a trigger returns true the chain

link nodes will then perform whatever

action that you tell the chain link

nodes to do we're also not going to go

over the chain link Keepers examples

right now because we're going to get to

them in a later module however if you

want to try them out go to docs. chain.

linkum going and go to making compatible

contracts and feel free to read the

documentation and try it out yourself

the last outof the-box feature of chain

link is the most customizable but also

the hardest to get correct end to end

reliability is the ultimate promise of

our smart contracts and we want and need

them to be able to do anything we want

to be able to take any input and get any

output chain link functions is the last

decentralized out of thebox tool and it

allows you to make any API call in a

decentralized context through a network

of chain link nodes we're not going to

be going over that at all in this video

but be sure to check out the

documentation if that's something that

you're interested in to me chain link

functions is going to be the future of

Defi and smart contracts and if you're

looking to make something novel and if

you're looking to make something that's

never been done before I 100% recommend

you check out chain link functions later

on after this course or whatever you

want to do as of filming it came out

about a month or two ago and people are

just beginning to build amazing things

with training functions so be sure to

check this out after or during the

course we're going to be using the chain

link Automation in a later section in

this course again if you want to try

these out in remix on a real test net

you can go to the documentation and play

with them

here now I know we haven't actually

written that much code but we've gone

over a ton so I want to do a quick

review in order for a function to

receive native blockchain token like

ethereum you need to mark that function

as payable if you want to force a

transaction to do something and you want

it to fail if that wasn't done you can

use a require statement a transaction

that reverts means it undoes any work

that it did previously and returns any

gas to the user to get the value sent

with a transaction you can use the

solidity Global message. Val chain link

is a technology for getting external

data and computation into our smart

contracts and most importantly getting

that data in a decentralized context in

this example we're going to be using a

chain link data feed or a chain link

price feed which is a decentralized way

to get pricing information from Real

World assets into our smart

contracts now in order for for us to

figure out if the amount of ethereum

sent with a transaction is greater than

or equal to our minimum USD of $5 we

need to convert the amount of ethereum

into its value of dollars so how are we

going to do that well the first thing

that we're going to need to do is we're

going to need to get the price of

ethereum or Avalanche or polygon or

whatever native blockchain token that

we're working with so let's create a

function to do that we'll create a

function get price and this function is

just going to get the price of ethereum

in terms of USD and then we're also

going to create a function called get

conversion rate rate which is going to

convert a value to its converted value

based off of the price for now we're

going to make them both public functions

so we can play with them test them and

do whatever we want with them to get the

price of ethereum we're going to use a

chain link data feed and we go through

the documentation to get that

information so in the documentation I'm

going to scroll down using data feeds

they've got an example here right and

solidity and if you wanted to like I

said you could easily open this up in

remix now you can see this example in

the documentation what's actually going

on working with a chain link price feed

there's a contract out there add an

address and we're going to call this

latest round data function on that

contract gives us a whole bunch of data

but we really only care about the price

so we're going to want to do the same

thing we want to reach out to that

contract that's currently storing and

having the price updated so since we

want to reach out to and work with the

contract we're going to need two things

right what are those two things well we

need the address and we need the AI the

address of the contract is going to be

really easy we can get the address by

going to the chain link documentation

and let's go to this price feed

addresses section

we'll scroll down we want to be on

ethereum okay great let's look for seia

looks like it's way down here and all

right awesome e2d great there's an e2d

price feed so now that we have the

address how do we get the ABI well

before with simple storage we imported

the entire contract from the top and we

compiled and we got the API like that we

could do that here but that's kind of a

lot of code and we don't actually care

about what the whole contract looks like

we only really want to know what the

functions are so we can call that latest

round data function remember if we're on

remix and we go down to the compilation

details the ABI is really just this list

of functions that we can call on a

contract the ABI itself doesn't actually

need to include any of the logic it just

needs to say hey these are the functions

you can interact with and here are their

inputs and here's whether or not they're

payable and here's whether or not their

view functions Etc like I said though

this kind of is a white lie you can also

use a function selector or some other

ways but we're just going to ignore that

for now how can we get the ABI there's a

concept in solidity known as the

interface if we go to the chain link

GitHub we go to smart contract kit /

chainlink we can see a lot of different

contracts in the chain link repository

we go to contracts SRC this might look a

little bit different based off of when

you're looking at it

v0.8 interfaces and we go to aggregator

V3 interface if we scroll down we can

actually see a whole bunch of function

declarations but none of them are

actually implemented it's just function

the name of the function some stuff

external view blah blah blah but then

just the semicolon and nothing inside of

them this is what's known as an

interface if you compile this this will

actually give us that ABI because it

defines all the different functions that

you can call on a contract it just

doesn't have any of the logic again we

don't really even need to know what the

functions do we just need to know how to

interact with the contract and if a

contract is deployed it'll have that

logic in its deployment so what we can

do is we can copy this whole thing

scroll all the way to the bottom hit the

copy button and paste it in our remix

now hold on though if you're following

along you don't have to copy paste it in

with me cuz I'm going to teach you

something in just a minute that makes

this a little bit easier this pasted

code alert comes up we're running

solidity code so this is going to be

okay since we're only working on test

Nets here we're going to be okay that we

don't have to worry about p a code alert

if you want to take a second to read it

please do but we're going to paste this

code in here just like we did before

with simple storage for now you don't

have to follow along I'm about to show

you an easier way just follow along and

watch now that we have this interface

aggregator V3 interface we can use this

interface to make API calls because now

we have the address and we have the API

and we can even compile this and it'll

compile fine so we can say aggregator V3

interface at address this and the

combination of these two give us

whatever code is at this address with

all the functions from the aggregator V3

interface and just to test this out we

can do something simple like dot version

since if we scroll up looks like there

is indeed a version function put a

little semicolon at the end so let's

actually go ahead and actually copy this

line give it its own function called get

version this we'll have this public view

Returns what is the version up here

return a un 256 return a un 256 paste

that line in here aggregator V3

interface at its address version we'll

say return all of that now I'm going to

go ahead and deploy this to the seoa

test net just to show you what this

would actually look like however I'm

going to recommend you don't do that for

now just know that this will work this

way you won't have to wait forever for

your transactions to go through on the

test net so to do this I'm going to go

ahead scroll to the top go to injected

metamask change the contract from

aggregator V3 interface to fundme going

to go ahead and hit deploy my metamask

is going to pop up I'm going to go ahead

and hit confirm and we're going to

scroll down and now we have a big blue

button called get version which I'm

going to go ahead and click and we can

see we get a four return because at this

contract address on the blockchain it

has the functionality for get version

returning 4 and for the rest of this

lesson I'm going to be showing you guys

and testing this on an actual test net

however I recommend that you don't test

all of these as I along just watch me do

them because again waiting for

transactions on a test net can be really

annoying sometimes a test net might be

having issues because again it's people

running them out of the goodness of

their heart so for this lesson just

follow along write the code with me and

then maybe at the end deploy everything

so this is a really easy way and a

common way that people use to interact

with other contracts outside of their

projects they get the interface of that

contract using the interface keyword

they compile it and the compiler

actually gives us an API and then you

just wrap an address around with that

interface keyword and you can call any

function at that address and and this is

one of these things as we work with more

and more it'll start to make more sense

in the beginning it might be a little

hard to grasp but just bear with me for

now the more we do it the better you'll

get don't get discouraged take a deep

breath and exhale and let's keep

coding and if this is confusing to you

this is again where we can work with our

AI friends or any of the forums that

we're working with again very soon I'm

about to show you how to ask really good

questions and make really good prompts

but one we could ask here is hey I'm

confused how does this solidity function

return the value four when I didn't

Define any logic in aggregator V3

interface and I just posted that code

from get version here because a common

issue that I see new developers run into

is they go oh wait wait how does this

version return four my aggregator V3

interface doesn't have any code in it

why why does putting an address in here

make it work like what's going going on

and let's see if our AI is able to help

us here so this is chat gbt version 3.5

again I prefer version 4 but this is the

cheaper one and it says in the code you

provided the get version function is

calling the version function of an

instance of the aggregator V3 interface

contract it appears that the contract

address here is being used to create an

instance of aggregator V3 interface the

aggregator V3 interface is an interface

contract that defines a set of functions

that must be implemented by another

contract it serves as a way to interact

with the contract at the given address

by providing a common interface the

version function being called in your

code is likely defined in the actual

contract that implements this uh and

this is pretty much correct right and so

it gives us some more context here this

is exactly correct this address has a

version function and US surrounding it

with this aggregative E3 interface like

typ casting it in these parentheses like

this is just telling our solidity

compiler hey there's a version function

at this address or there's a latest

round data function or all the functions

all the functions in this aggregator V3

interface are at this address if this

address doesn't have a version function

this would just break and this is a good

example of again where we can actually

follow up with these AIS they're

typically very good at keeping context

so we could even ask what would happen

if that contract address didn't have

that

function and we see if the

implementation contract at the given

address does not have a version function

or if it has a different function

signature calling version on the

contract would result in a compilation

error or a runtime error so it wouldn't

result on a compilation error but the

transaction would revert so so this is

pretty helpful here but again we always

want to double check this so this is

where we'd probably go back to the

discussions forum and follow up

there so now that we actually have the

interface we can start calling these

functions and calling these addresses

however having a ton of these interfaces

is really going to clog up our contracts

and clog up our files and be really

gross to work with is there a better way

for us to do this well when we worked

with simple storage yes there was we

just went ahead and used Imports right

but that's when we had all the code in

our locally in our directory we don't

have all the code locally we didn't

create the aggregator V3 interface we

didn't create the price feed contracts

so can we do something like import

simple storage. but with a contract

outside of our project well again we

could copy paste it to its own file and

import add k T V3 aggregator V3

interface. so and of course we're going

to use this named import syntax because

we're awesome developers we could copy

paste it like this and do exactly what

we did before we could create a new file

called aggregator V3 interface paste the

code in there or we could actually

import directly from GitHub if we go

back to the documentation associated

with using data feeds we scroll down to

using data feeds here scroll down we see

at the top they do this import like this

import at chainlink contracts as C blah

blah blah this import actually has the

same setup as as the path of what's in

the GitHub repository so instead of us

copy pasting from GitHub we can actually

import directly from GitHub or mpm we

can copy this line back in our remix we

could paste it in like this remix is

smart enough to know that this at

chainlink contracts is referring to the

what's known as an mpm package chainlink

contracts chainlink contracts is what's

known as a package manager and it keeps

different versions of combinations of

code for us to download at chainlink

contracts is created directly from chain

link repository remix downloads all this

code from mpm which is Created from the

GitHub so it essentially downloads it

from the GitHub so us doing this import

like this is the same as is just copy

pasting the entire interface at the top

of our contract now we have this

aggregator V3 interface that we want to

work with we can go ahead and compile

and bada bing bada

boom so great so now that we have the

interface here which will give a

minimalistic ABI for us to interact with

the contract how do we actually get the

pricing information well again if we go

back to the docs we can see right here

gives us an example of the code we can

use to get the latest price but let's

write it ourselves just so that we know

what's going on we'll say agregator V3

interface and we'll actually create a

new variable called price feed equals

aggregator V3 interface contract at this

address which again only works for

sapoia now we can call this latest round

data function on the price feed so we'll

say price feed. late round data and if

we look at the interface on GitHub we

can actually see latest round data

doesn't just return one variable it

returns a whole bunch of different types

of variables and to return multiple

types we do some syntax that looks like

this and we'll say uint 80 round ID and

you can even flip back and forth between

the documentation make sure you have it

right int price which again we know in

int defaults to an INT 256 you uint 256

started app uint 256 Tim stamp and then

uint 80 answered in round there's a lot

of code in here since this function

returns so many variables we have to set

something up to capture them but we

don't care about any of these other

stuff we just care about price so what

we can do is actually just remove them

and leave the commas in there so we're

going to remove started at remove time

stamp remove answered and round and I

hit command s to compile we're going to

get these yellow squiggly lines which

are warnings but we're going to fix them

in a minute now we have in price equals

Price feed. latest round data because we

only care about getting the price from

the return the reason price is an into

56 is because some price feeds could be

negative now that we have the price this

price variable is going to be

representing the price of eth in terms

of USD and it's going to return a number

that looks like this because again slity

doesn't work with decimals so we know

that this price feed has eight decimals

but it'll get a return like this boom

like this it'll return a value that

looks like this

if we want to double check how many

decimals there are in a price feed it

actually has a decimals function which

allows you to check that as well now as

we know message. value is going to have

18 decimal places how do we know that

well because we know that one ether is

equal to this many way and this many way

has 18 zeros 1 2 3 4 5 6 7 8 9 10 1 2 3

4 5 6 7 8 so this massive number is

equal to 1 ethereum right 1. 1 2 3 4 5 6

7 8 9 10 1 2 3 4 5 6 7 eight so right

now message. value and price actually

have different decimal places price has

eight message. value is going to have 18

so to get them to match up we have to do

return price times 1 E10 or to add those

additional 10 decimal places and yes I

know we have a red line I'll fix this in

a minute price as we know is a in 256

and message. value is going to be a u

256 so the types are actually different

so we want to get the price and terms of

U 256 instead of in 256 to convert them

we can again do a thing called type

casting there are a lot of different

types that can be easely converted

between each other not all types can be

typ casted but an INT and a un 256 can

be so to make our price a u 256 we would

just do uint 256 and wrap price like

this or we could just wrap both of them

like this now of course since we're not

modifying any state but we are reading

storage we can make this a view function

and then we'll say it returns a uint 256

like so now if we compile we get rid of

all those errors and warnings now math

could be a little bit tricky in solidity

but the more you do it the better you'll

get and the reason math can be tricky is

because there aren't any decimal places

so you need to only work with whole

numbers the more you work with it the

better you'll get

though awesome so now we have a get

price function which is going to return

the value of ethereum in terms of USD as

a u 256 now all we we have to do is

convert our message. value in terms of

dollars using this get price function to

do that we're going to use our get

conversion rate function this get

conversion rate function is going to

take a u 256 eth amount as an input and

we're to convert this eth amount to its

value in dollars this will be a public

view function that will return a uint

256 so first we're going to get the

price of ethereum by doing U 256 e price

equals our get price function that we

just defined and then we're going to do

U 256 eth amount in USD equals eth price

time eth amount and then we actually

have to divide by 1 E18 the reason we

divide by 1 E18 is because both of these

have 18 decimal places and if we

multiply 1 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7

8 9 10 if we multiply these by each

other where both of these are

representing one we're actually going to

get a number that's absolutely massive

with 38 decimal places so we need to

divide by 188 to reduce it back down to

what it should actually be an important

rule with working with math and solidity

is you always want to multiply before

you divide the reason for this is since

again only whole numbers work in

solidity you were to do 1 iD two you

would end up getting zero so you always

want to multiply first when we get to

the foundary section of this course

testing all this math is going to be a

lot easier if you're really struggling

with some of the math bits right now I

wouldn't let that slow you down because

one of the things that AI is really good

at is doing a lot of these math

conversions but in any case this eth

amount in USD is the number that we're

looking for so we can say return e them

out in USD and awesome now we have a get

conversion rate function let's walk

through this together just so that you

can understand what's actually going on

let's say we want to see how much one

eth is worth well we're going to get the

eth price which let's say it's $2,000

but it's going to be $2,000 with one2 3

4 5 6 7 8 1 2 3 4 5 6 7 8 9 10 18 zeros

so e might look something like this so

that means we're going to do this 2,000

with 18 decimal places times 1 E which

is going to be 1 1 2 3 4 5 6 7 8 1 2 3 4

5 6 7 8 8 9 10 we're going to multiply

those together and then since we're

going to get an additional 36 zeros then

we just divide by 1 E18 and that's how

we would get

$2,000 equals 1 E it's going to be 2,000

of course with 18 decimal places one of

the good reasons for using whole numbers

in solidity is that it's not possible to

have decimal places so we don't lose any

Precision which is really good so

normally we should test this function

before continuing but since we're doing

all this on a test that and I promise

you that I tested this all beforehand

we're just going to go ahead and keep

going so now that we've done all this

work if we want to make sure that our

users are sending at least $5 we can do

get conversion rate of message. sender

needs to be greater than minimum USD

because get conversion rate takes an eth

amount as input uses the price pricing

information to get the dollar value back

and we're going to check to see that the

dollar value of the message. value is

greater than the minimum USD however

since get conversion rate returns a

value with 18 decimal places we need to

update our minimum USD to say 5 * 10

raised to the 18th or we could also do 5

E18 or we do 5 * 1

E18 I personally like this 5e8 syntax

but whatever works for you I'm going to

deploy this to a test net just to

demonstrate this working but again you

do not have to so we're going to go

ahead delete our previous deployments

injected web 3 deploy metam Mass pops up

going to go ahead and confirm after a

long delay we'll get our deployed

contract here we have all this stuff we

can call get price and we can see the

value of ethereum right now is this with

18 decimal places which is awesome so

it's around

$1,896 so if I were to try to fund this

with maybe 100 way I know for a fact

that way isn't going to be enough so if

we call this fun function we're actually

going to get this gas estimation failed

gas estimation error failed with the

following message blah blah blah error

execution reverted didn't send enough

eth which is actually exactly the error

message that we have here it's exactly

what our error message is here in our

require didn't send enough eth so if we

try to fund it we're going to get didn't

send enough eth and this gas estimation

failed is a pretty common error that

you'll see in remix and solidity and evm

in general it's kind of just the boiler

plane answer for something went wrong

luckily we got the actual error message

here so we could debug here's what's

actually going on now you see here we

could still send this transaction like I

said we would actually spend gas to send

a failed transaction and this isn't

something that we want to do so we're

going to go ahead and cancel however if

we did send maybe 1 1 2 3 4 5 6 7 8 1 2

3 4 5 6 7 8 9 so if we go to Google

actually we can even see like an e to

dollar conversion rate so if we sent

0.01 0.01 eth right now is worth $8

dollar it might be different depending

on when you actually do it so we send

0.01 e in our remix and we can do that

by doing 1 1 2 3 4 5 6 7 8 9 10 1 2 3 4

5 6 so it's 1 e16 and we hit fund now we

actually see metam Mass pops up we don't

get that gas estimation error we can go

ahead and confirm and we can see that

our function is working as expected

which is great it's reverting

transactions that have less than $5 and

it's letting transactions go through

that have at least $5 awesome and if we

select minimum USD we can obviously see

that here and we can see we have 0.01

eth here fantastic and since we don't

have a withdrawal function here we

actually can't pull it out which is

another reason why I say hey maybe don't

test this right now but great we've

confirmed our get conversion rate is

working so let's move on

fantastic so what's the next thing that

we should do in this contract well we

probably want to keep track of the users

who send us money in this contract so we

can keep an array of addresses called

funders and keep updating that depending

on who actually sends US money so up at

the top we'll make an address array or

an address list we'll make it public and

we'll call it funders and anytime

somebody sends US money we'll say

funders do push message. sender like

message. Val message. sender is another

Global variable we can use in solidity

which refers to whoever called this

function the sender of the transaction

to this contract so if we're on sapoia

and we initialize a transaction for a

metamask the message. sender is going to

be this account right here and then

maybe we want to even make a mapping of

addresses to to make it easier to look

up how much money each funer has sent so

we'll make a mapping of an address to a

u into 256 we'll call it public address

to amount funded now something that's

newer in solidity is you can actually

name the types in your mapping so you

could say address fun mapped to un 56

amount funded usually this is what's

known as a little syntactic sugar it's

just to make it easier to read what this

mapping is Right fun to amount funded

and then our variable name is very

explicit address to amount funded now if

somebody funds our contract we'll of

course do address to amount funded the

message. senders address plus equals

whatever they previously have funded

Plus message. value whatever they're

additionally adding all right great and

now we have a way for us to keep track

of funders sending money to our contract

and have an easy way with a mapping to

look up how much they've spent in

total now I know we've gone over a lot

of advanced solidity here so let's do a

quick refresher of what we've learned so

far whenever we interact with a contract

we always need the address and the ABI

compiling an interface allows us to get

that ABI very easily for us to interact

with another contract when we combine

the contract address with the interface

we can easily call the functions on that

contract chain link price feeds are an

easy way to get data especially pricing

data from The Real World into our smart

contracts when working with math in

solidity and the evm in general decimals

don't work so we need to always make

sure we're using the correct number of

units whenever we interact with our

contracts message. value and message.

sender are known as globally available

units in solidity and they refer to the

send a of a message of the current call

or the number of way sent with a message

or transaction there's a whole bunch of

these and you can view them all in the

solidity

documentation all right great so we've

got a way to actually get this pricing

information pretty easily however our

code is getting a little bit cluttered

with these get price and G conversion

rate you'd think that these are

functions that would be reused pretty

often anyways for anybody looking to

work with chain link price feeds so is

there an easier way for us to work with

this pricing information maybe doing

some math like this is pretty common and

we'd want other contracts to be able to

import this conversion functionality and

a way that we can do that is actually

creating something called a library

there's a site out there called solidity

by example which has great examples of

using libraries and what they work with

libraries are similar to contracts but

you can't declare any state variables

and you can't send ether a library is

embedded into the contract if all

Library functions are internal otherwise

the library must be deployed and then

linked before the contract is deployed

that's a little bit confusing don't

worry too much about that right now

using libraries can actually add

functionality to different values and

what do I mean by that well I mean we

can have our get conversion rate

function be a function of any value of

type you 256 means we could take this

get conversion rate and do something

like message. value. getet conversion

rate so we can create our own custom

function with any type we could work

with get conversion rate as if message.

Val was a class or an object or a

contract that we actually created to do

this let's go back to our files create a

new one create a new one called price

converter

soul and this is going to be a library a

price converter Library so how do we

create a library and what is a library

well a library is going to be very

similar to a contract we're going to

start of course with spdx license

identifier we're going to do pragma

solidity and we'll give it a version of

0.818 the little carrot and instead of

typing contract we're actually going to

type library for the name of the library

and we're going to call this Library

price converter so libraries can't have

any state variabl and all the functions

have to be marked internal so what we're

going to do is we're going to go back to

fundme doso zoom out a little bit we're

going to grab get price get conversion

rate and get version delete them well I

hit copy first go back to price

converter paste them in here and work

with them in here of course we're going

to need the aggregator V3 interface so

we're going to go back to our funme

we're going to copy this named import

from aggregator V3 interface paste it in

at the top here hit command s and we're

going to go ahead and compile this

successfully fundme is no longer going

to compile but we're going to fix that

in a little bit now the first thing that

we're going to need to do in here is

make these all internal so we're going

to say internal like this we do internal

get conversion rate and internal get

version now that we have our price

converter Library we can actually import

it back in our fundme and attach it to a

un 256 and let's actually delete this

aggregator V3 interface line for now and

we'll do import price converter

fromprice converter do soul and now to

attach the functions in our price

converter library to All U 256s we'll

say using price converter or uint

256 of course if we compile our fundme

we're going to get an issue because it

doesn't really know what get conversion

rate is so for now let's actually just

comment out this line I'm going to

remove these comments up here as well so

what we can do now though is we can do

message. value. getet conversion rate

get conversion rate and in your library

whenever you're working with a library

the first input variable for a library

is going to be the type that you're

using with the library so message. value

is of type un 256 so this gets passed

inside of get conversion rate as the

first variable into U 256 e amount even

though we don't pass any variables

inside of these parentheses here for get

price and get version we don't really

care to have an input parameter at all

so it'll pass it in but not do anything

so now instead of require get conversion

rate of message value we can actually do

let's uncomment this line now and let's

delete this line we can actually do

message. value. getet conversion rate

conversion rate and now if we compile

this this is going to compile

successfully this works because we're

attaching the price converter library to

all un 256s so now all un 256s have

access to this get conversion rate

function and since message. Val is a un

six it can call. get conversion rate and

it'll pass itself so that message. value

as the first input parameter to the

function here if we wanted another

variable in here like U into 6 something

else that would be the first parameter

inside these parentheses so maybe like 1

2 3 or something right this one 2 3

would be the something else but message.

value would still be the initial

parameter which in this example would be

eth amount so let's go ahead and undo

that and undo that but all right great

we've moved a lot of the math into our

own Library congratulations nice

work one of the most common libraries

that was used for a long time was this

Library called safemath dossou and in

your solidity Journeys you'll probably

see it pop up from time to time now

we're going to go off on a little bit of

a tangent here about safe math and the

library safe math and this is an excerpt

from my course last year so you might

see stuff like rink B and some other

stuff but just focus on the safe math

stuff just know when we refer to the

JavaScript virtual machine that's

talking about the remix virtual

machine one of the most common libraries

that was used for the longest time was

this Library called safemath dossou and

you'll probably see it a lot of

different places we're going to go off

on a quick little tangent here and teach

you about safe math so let's close

fundme and close price converter and

let's create a new file called safe math

tester. soul and let's start with some

basic stuff in here safe math was all

over over the place before version 0.8

of solidity and now it's almost in no

contracts what happened why is safe

maath no longer used as much well let's

create a sample contract this is a

section that you don't have to follow

along if you don't want to code along

with me but if you want to you

absolutely still can this is going to be

a contract we are going to deploy on a

JavaScript virtual machine uh we can use

any version of solidity before version

0.8 of solidity so for example we'll use

pragma carot 0.6 6.0 and we'll create

contract safe math tester. Soul now if I

create a un 8 I set it to

public big number and I set this to

255 oops safe math tester let's go ahead

and compile safe math tester with

0.67 fragma solidity the maximum size of

a u 8 is going to be 255 this is going

to be the biggest number that we can fit

in an U 8 and if I were to deploy this

to a JavaScript VM or even a test

Network save math tester let's go ahead

and deploy

it if I hit big number we're going to

get

255 well what happens if I create a

function called add that sets big number

equal to big number + one let's save

that delete that old contract and deploy

right now big number is 255 what happens

when we add one to big number when 255

is the max size a uint 8 can be well

let's hit add now let's check what big

number is big number gets reset to zero

so what's going on well prior to version

0.8 of solidity unside integers and

integers ran on this concept of being

unchecked which means that if you passed

the upper limit of a number it would

just just wrap around and start back

from the lowest number it could be so if

I call add a whole bunch more times and

hit big number now it's eight if I were

to hit this add button a ton more times

and get it back to 255 it would then

continue to wrap over to zero so one of

the most popular libraries that was out

there was this safe math Library which

would basically check to make sure that

you weren't wrapping around a un 256 or

an in 256 basically it was a way to say

hey you've reached the max this number

can be and now your transaction is going

to fail if we switch this to 0.8 of

solidity delete the old contract go

switch this to

0.8 we'll go ahead and compile it and

now we deploy this to JavaScript

VM if I hit big number we get 255 but if

we hit add it actually fails and we

still get 255 in version 0.8 of solidity

they added this bit where it

automatically checks to make sure if

you're going to do what's called

overflow or underflow on a variable we

can actually revert back to the

unchecked version by using an unchecked

keyword so if we wrap this big number

equals big number + one in this

unchecked bracket let's delete our old

contract we'll compile we'll

redeploy we hit big numbers 255 now we

hit add we hit big number again it

reverted back to zero so that's a little

bit more about safe math checked and

unchecked so version 0.76 and below this

code that you see in front of you is

going to be the exact same as this code

in 0.8 and above with this unchecked

keyword now you might be thinking in

newer versions of solidity why would I

use this unchecked keyword well you'll

find out later that this unchecked

keyword makes your code a little bit

more gas effici so if you're absolutely

positive that your math is never going

to reach the top or bottom limits of a

number then might make sense for you to

use the unchecked keyword let's head

back over to our fundme contract where

we are now using the price converter

library that we just

created awesome we have a lot of the

basics of the math that we need in our

fundme contract it's all right so this

is great people can actually send us

money and we're going to keep track of

them as well which is fantastic so the

next thing obviously that we're going to

want to do is we're going to want to be

able to withdraw that money out so now

let's go ahead and Implement our

withdraw function when we withdraw all

the money we're probably going to want

to reset all the mappings back down to

zero to show that hey we've withdrawn

all the money and there's nobody left to

do this we're going to use something

called a for Loop a for Loop is a way to

Loop through a list of something or to

do something in a repeated amount of

time if you're familiar with other

programming languages it's the exact

same concept we wanted to get all the

elements in this list for example which

where one is at the zeroth index two is

at the first index three is at the

second index and four is at the the

third index which I know is a little bit

confusing these are the different these

are the indexes these are the elements

we would Loop 0 through three to get all

the elements out of this array to do

this loop we're going to use the four

keyword we're going to say four put some

parentheses and in a for Loop we can add

a couple things and by the way this is a

way to do comments inside of a line and

solidity you do a back slashstar star

back slash and now everything in here is

a common so in a for Loop you first need

to give it the starting index then you

give it the ending index and then you

can give it the step amount for example

let's say we want to start on the zeroth

index we want to go all the way up to

the 10th index and we want to go by up

each time we would do 0o 1 2 3 4 Etc

well let's say we want to start with the

third index we want to go to the 12th

index and we want to up by two every

single time well we would do three five

7 9 Etc so our starting index is going

to be a un 256 and we'll call it under

index and we're going to say we're going

to start with zero and we're going to

end once the funer index is less than

the funders length so I know I said up

here it's the ending index but instead

it's a Boolean once the funders index is

greater than fund. length which is how

you can get the length of an array then

we're going to end and then finally

we're going to say every single time we

do a loop we're going to say funders

index equals funders index + 1 now

there's a shortcut you can do to do some

variable equals itself + 1 and that's

just Plus+ this plus plus means every

time we go through the loop just add one

and we actually don't need that here and

then we put these curly braces to say

okay execute everything inside of this

Loop here for the duration that we

specified here and this final piece

means that every time we run through all

the code inside of these brackets we're

going to add one to this funders index

that's how we go from0 to 1 2 3 4 5 6 7

Etc to access the zero withth element of

our funders array we're going to say

funders of fun index and this is going

to return an address since it's an array

of addresses so we'll say address fun

equals funders of funer index and we

want to use this to reset our mapping

address to amount funded so we can say

address to amount funded at the funer

address is now equal to zero so we're

going to reset whatever we add added

when they funded us down to zero because

we're withdrawing all the money out and

additionally how there's a nice little

shorthand like plus plus down here up

here in the fund another nice little

shortcut whenever you want to add

something to whenever you want to add

something to something that already

exists instead of doing something equals

itself plus the new thing you can just

do plus equals this means that we're

going to set address to amount funded of

message. sender equal to itself Plus

plus message. Val so let's walk through

this for Loop a little bit we're going

to start with the zero withth index

we're going to get the fun at the zero

with index in our funer array we're

going to take that address stick it into

our mapping and reset the amount that

they've sent us to zero then we're going

to do funer Plus+ we're going to check

to see that funer plus funer index Plus+

is less than funders do length obviously

fun 0 + 1 is going to be one so we're

going to check if one is less than the

total amount of fun fers and then we're

going to get the address of the fun at

the first index reset them to zero get

the address at the second index reset

them to zero third index etc etc until

we finally reach the index that is equal

to or greater than the length so if we

have 10 funders and we reach funer index

10 the for Loop will exit and be

done but we still haven't done two

things we need to reset the array still

and then we also need to withdraw the

funds since we've accumulated all this

message. Val in the fund function to

reset the funders array we could do the

same thing we did with the mapping and

reset each single address at each index

or we could just create a brand new

funders array which is what we're going

to do so to reset the array we're now

going to say funders equals new address

array and to start off at a length of

zero previously we used the new keyword

to deploy a different contract now we're

using the new keyword to reset the

funders array to a brand new blank

address array this part is a little

confusing don't let it hold you back and

lat later in the course why we make the

choices here that we do so great we've

gone ahead and reset the array so now

how do we actually withdraw the funds

for this section I'm going to go ahead

and again refer to a previous course

that it did because the content is

exactly the same just remember

JavaScript VM is remix VM

so great we've gone ahead and reset the

array but how do we actually now

withdraw funds from this contract how do

we send the funds back to whomever is

calling this now to actually send ether

or send native blockchain currency there

are actually three different ways to do

this we're going to look at all three

and say what the differences between the

three of them are the three different

ways are going to be

transfer send and call let's go ahead

and start with transfer since transfer

is the simplest and at surface level

makes the most sense to use so if we

want to transfer the funds to whomever

is calling this withdraw function we

would do we would say message.

sender.

transfer and then we'd get the balance

of our contract here by saying

address this the this keyword word

refers to this whole contract. balance

and we can get the native blockchain

currency or the ethereum currency

balance of this address like this and we

can just do that only thing that we need

to do is we need to cast we need to typ

cast message. sender from an address

type to

a payable address type so message.

sender is of type

address whereas payable

message. sender is of type payable

address and in solidity in order to send

the native blockchain token like

ethereum you can only work with payable

addresses to do that so we just wrap it

in this payable typ Caster so this is

the first way that we actually send

ethereum or send tokens from different

contracts to each other we wrap the

address that we want to send it in in

this payable keyword we do transfer and

then we say EX exactly how much we want

to transfer but there are some issues

with transfer here we are on solidity by

example for sending ether which again is

a fantastic resource to refer to if you

get lost the method that we just looked

at was this transfer method now we saw

way earlier in the course that if I sent

ethereum from one address to another it

cost about 2100 gas or 2,100 gas our

transfer function is capped at 2300 gas

and if more gas is used it throws an

error the next one that we're using is

going to be send which is also capped at

2300 gas and if it fails it'll return a

Boolean so with transfer if this line

fails it'll error and revert the

transaction with send it won't error

it'll return a Boolean of whether or not

it was successful so using send will do

pay

message.

sender.

send address

this balance but we don't want to finish

our call Here If This Were to fail the

contract wouldn't revert the transaction

and we just wouldn't get our money sent

so we want to do Boolean send

success equals this whole bit here and

then we want to require send success and

if this send fails we'll throw an error

saying send

failed this way if this fails we will

still revert by adding our require

statement here transfer automatically

reverts if the transfer fails send will

only revert the transaction if we add

this required statement here so great

what's the third way that we can

actually send ethereum or native

currency well it's with this call

command Now call is going to be one of

the first lower level commands that we

actually use in our solidity code

because this call function is actually

incredibly powerful and we can use it to

call virtually any function in all of

ethereum without even having to have the

ABI we'll learn the advanced ways to use

this call much later for now we're just

going to learn how to use it to send

ethereum or your native blockchain

currency call is going to look very

similar to send we're going to do

payable

message.

sender. call and this is where we'll put

any function information or any

information about the function we want

to call on some other contract we

actually don't want to call a function

so we're going to leave this blank we

can show that we're leaving it blank by

just putting in these two quotes here we

instead want to use this like a

transaction and as we saw in our

deployment there's always this message.

value bit so we're going to use this

call function as if it's a regular

transaction and we can add stuff like

message. Val so in here we're going to

add these squiggly brackets and we're

going to say

value

address

this

balance this call function returns

actually two variables and when a

function returns two variables we can

show that by placing them into

parentheses on the left hand side the

two variables it returns are going to be

a Boolean that we're going to call call

success and also a byes object called

Data returned since call allows us to

actually call different functions if

that function returns some data or

Returns value we're going to save that

in the data returned variable it also

returns call success where if the

function was successfully called this

will be true if not this will be false

and since bytes objects are arrays data

returns needs to be in memory now for

our code here we're actually not calling

a function so we don't really care about

data returned so similar to what we saw

with the price contract we can just go

ahead and delete that and leave the

comma to tell solidity yeah we know this

function returns two variables but we

only care about one and then similar to

the send piece above we're going to do

require call success call failed meaning

that we're requiring call success is

true otherwise we'll revert with an

error that says call failed now if

learning the difference between these

three is a little complicated for you

right now don't let that slow you down

feel free to come back to this after

you've learn more about how some of

these lower level functions work and a

little bit more about how Gas Works

solidity by example does a fantastic job

though of saying what the differences

between all three are transfer has a

maximum of 2300 gas and throws an error

if it fails send has a maximum of 2300

gas returns a Boolean if it fails call

forwards all gas so doesn't have a

capped gas and similar to send returns a

Boolean if it is successful or if it

fails as of recording right now using

call is the recommended way to actually

send and receive ethereum or your

blockchain native token for now if this

part's a little bit confusing for you

for now now just look at this and see Ah

that's how we send and transfer ethereum

or native blockchain currency tokens and

I'm going to delete this part for the

video but but I'll keep those comments

in the code repository associated with

this

course all right great and actually the

exact same code from that video we're

going to use for this as well so we're

going to use this call call success to

work with sending a balance however

there's a bit of an issue here right now

anybody can call this withdraw function

and take all the money out of this

contract we don't want that we want

anyone to be able to fund the contract

but we don't want anyone to be able to

withdraw money from the contract we only

want the owner of the contract to be

able to withdraw so how do we set this

contract up so that the withdrawal

function can only be called by the owner

of this contract well we want to set

this contract up so that whenever we

deploy it whenever we create this

contract an owner gets assigned to this

contract we assign some address to being

the owner and then then we add some

parameters so that withdraw can only be

called by that address so what we could

do is we could set up some function

called call me WR away and when we

deploy this contract we would just

immediately call this call me RightWay

function which will set us up as the

owner however that would take two

transactions and remember we're

Engineers we want to work incredibly

hard to be incredibly lazy so instead

solidity has something called a

Constructor and if you're familiar with

other programming languages a

Constructor is the exact same as really

every other programming language and the

Constructor is a keyword and a special

function in solidity so we can create a

Constructor function without the

function keyword we just call it

structor and we also don't even need the

public keyword you'll see remix even

highlights it pink this is going to be

that function it's going to be a

function that is immediately called

whenever you deploy your contract this

function will be called in the exact

same transaction that is used to deploy

your contract for example if I were to

take this minimum USD added in our

Constructor and say minimum USD equals 2

this minimum USD would immediately get

updated to two right after this contract

is deployed in that exact same

transaction since we want this

withdrawal function to only to be able

to be called by the owner of this

contract in our Constructor we can set

up an address right away to be the owner

of this contract so let's create a

global variable called address public

owner and then right in our Constructor

we'll say owner equals message. sender

message. sender of course being the

sender of the caller which in this

example is going to be the deployer of

the contract don't worry we're going to

demo all of this very soon to show you

everything that's going on if you want

to test all this right now absolutely go

for it just remember it's going to take

you a little bit longer on a test net

and I'm going to show you how it all

works anyways now that we have our owner

set up we can actually modify our

withdraw function so that only the owner

can call this function easily enough

we're already familiar with the require

keyword we could add a require the

message. sender of whoever calls this

withdrawal function must be equal to and

this is how you do equals in solidity

with this double equal sign a single

equal is set a double equals means

equals so message. sender must equal the

owner and if it's not the owner we could

revert with something like must be owner

awesome so now we have a quick way to

require that whoever calls the

withdrawal function is indeed the owner

awesome

but let's say we have a lot of admin

functions or only owner functions or

functions that should only be called by

the owner would we have to put this line

on every single function remember we

want to work incredibly hard to be

incredibly lazy we don't want to have to

copy paste this line to every one of

these functions and this is where

something called modifiers come into

play so we're going to go ahead and

actually delete this line and at the

bottom we're going to create our first

modifier a modifier is going to allow us

to create a keyword that we can put

right in the function declaration to add

some functionality very quickly and

easily to any function to create a

modifier you use the modifier keyword

and then you set it up very similarly to

a function so our modifier is going to

be called only owner we don't give it a

visibility like functions and in here we

can put our code so again we'll say

require the message. sender is equal to

not set to is equal to the owner and if

it's not the owner we're going to say

sender is not owner like this and then

underneath we're going to put this

little underscore with a semicolon what

we can do is we can take this only owner

keyword and stick it in the function

Declaration of our withdraw and what's

going to happen now is it's going to

execute what's in this modifier first

it's going to execute this require and

then this little underscore says and

then add whatever ever else you want to

do in the function so we're going to

execute this require then whatever else

is in the function and for our withdraw

a function it's going to be everything

else in here in our modifier if we had

the underscore above the require this

means that we would execute the code

inside the function first and then the

require so the order of your underscore

matters so now with this modifier

keyword in the withdraw function

whenever you call the withdraw function

we first go up there's a modifier I got

a drop down here we'll execute this oh

here's an underscore time to go back to

the function let's do what else is in

the rest of the code and then it'll come

back down to the only owner modifier and

say oh is there anything else to do oh

there's nothing else so I guess we're

good so let's see this all go through

end to end and remember you don't

actually have to deploy this to a test

net if you don't want to but if you want

to follow along feel free to do so of

course as well get started let's of

course compile file fundme Doo looks

good let's delete any contracts deployed

previously let's make sure we're on

injected provider menam mask and let's

make sure that we are on a test net we

are indeed let's make sure we have a

little bit of test net eth in our wallet

and we sure do and let's go down to the

contract and make sure we're on the

right contract if you try to deploy some

like an interface you'll get an alert

like this this contract might be

abstract blah blah blah so we're not

going to do the interface we're going to

do the fundme contract of course we'll

hit deploy metamask will pop up we'll go

ahead and hit confirm on the metamask

and then we're going to have to wait a

little bit for the contract to actually

finish deploying if we pull up the

terminal we can see the contract go

through and we can also see it in remix

here now we've got a number of buttons

in here we've got our red fund button of

course which is because we have our fund

function which is payable and this

allows us to send eth with this function

we have our withdrawal function which is

just orange because it is not payable

although it is going to be withdrawing

money out of the contract and then we

have our typical blue View and pure

functions the owner of course is going

to be our metamask since we are the ones

who deployed this contract minimum USD

is going to be five and these are of

course going to be empty we can call our

fund function only if we send some value

with it if we try to call fund without

any value we're going to get this gas

estimation error failed and we'll even

see didn't send enough eth in the ER log

so let's go ahead and cancel this again

we could send this but that would be a

huge waste of gas so we'll cancel it and

let's get a value that's going to be

enough so I believe 0.01 eth should be

enough let's say 0.01 eth it looks like

that's about $18 so back in remix let's

do 0.01 e in terms of wayy which is this

value here paste that in

and we'll scroll down now if we call

fund it does indeed go through and we

can go ahead and hit confirm on this as

well and we see that transaction pop up

on ether scan and we might have to wait

a little bit for this transaction to

finish finish going through finish

indexing Etc so let's give it a couple

minutes oh looks like it's gone through

fantastic we can even see in the fundme

contract the balance has gone up to 0.01

and we can see if we look at funders at

index zero we can see our address and if

we copy our address and paste it into

the mapping address to amount funded we

do indeed see an amount in here with

this transaction fund being called of

course on The testnet Ether scan we can

see all the data and information

associated with this and we can even

scroll down and see the input data we

can see that this was calling the fund

function we'll learn more about the

input data later so now we could do is

we could do the reverse we could go

ahead and withdraw and that should reset

the mapping and the array back down to

zero for our modifier to work we have to

use withdraw on this account if we

switch to an account that isn't the

owner of this contract and we go ahead

and reconnect and we scroll down we make

sure value is zero and we scroll down

and try to hit withdraw we'll see we get

gas estimation failed and we'll even say

sender is not the owner so we'll go

ahead and cancel that we'll switch back

to account one we'll make sure we're

working with account one now we'll call

withdraw we'll see ass does indeed pop

up and we can go ahead and confirm and

in just a minute we'll see the balance

reset and if we call our funders and

mapping they should also have been reset

so let's wait a little bit now if I try

to call address to amount funded with

that same address we now get zero and

now if I look at funders at index zero

it actually airs and this isn't

correct following our more advanced Lo

Concepts if you don't understand them

the first time don't let them stop you

they're not required to know to continue

the following is an excerpt from a

slightly older edition of this course

you'll see that I don't use named

Imports like a noob and a few other

pieces of the code look slightly

different but this next section we're

going to go over a lot of really

Advanced solidity pieces here that are

going to really Advanced solidity

fundamentals these are going to be

fantastic for saving gas making your

code look a lot cleaner and just better

coding practices overall for those of

you who are looking to go super far with

this definitely be sure to pay attention

to this section because this will make

you look like a bad as when you code

later on just remember when we say

JavaScript VM we just mean remix VM

additionally whenever we deploy to the

rink B test net just know that you

should be deploying to theoa test net or

whatever the most upto-date test net is

or just don't deploy to the test net and

just follow

along we're going to modify this

contract to make it a little bit more

professional it's not going to be end to

end amazing but it's going to be a

little bit better and you'll see why in

a minute so the first thing that we're

going to do is we're looking we're going

to look at some of these variables here

in particular owner and minimum USD

owner gets set one time in our contract

here and then it never changes again

minimum USD gets set one time even

outside of the Constructor if we have

variables that only get set one time we

can actually use some tools and solidity

to make them more gas efficient for now

let's compile our fundme contract and

then deploy it to a jscript virtual

machine remember we can go ahead and

deploy it right now however ever funding

and withdrawing and doing any of the

money stuff isn't going to work because

again we don't have a chain Lake Network

on our JavaScript VM so those aren't

going to work so well but for what we're

going to do right now we don't really

care so much here's what we do care

about we do care about how much gas this

costs to actually send we do care about

how much gas this costs to create right

now creating this contract costs about

$859,000 gas and we're going to add a

couple of Tricks right now to bring this

number down we're going to add some

stuff back in in a bit which will bring

it back up but for now we're going to

learn some tricks to bring this number

down the two tricks that we're going to

learn are the constant keyword and the

immutable keyword in their solidity

there are two keywords that make it so

that your variables can't be changed and

those keywords are constant and

immutable you can learn more about them

in the solidity documentation if you

assign a variable once outside of a

function and then never change it so if

if it's assigned at compile time you can

go ahead and add this constant keyword

we'll learn later about storage but when

you add a constant keyword this minimum

USD no longer takes up a storage spot

and is much easier to read to so now we

recompile this and we deploy this new

contract let's see if we saved any

gas we look in the transaction logs now

we can grab the transaction cost of how

much this cost to deploy and let's

compare it to how how much it was before

wow we saved almost 19,000 gas that's

almost as much gas as it cost to send

ethereum typically constant variables

have a different naming convention

typically you'll want to do them all

caps like Min eum underscore USD so all

caps with underscores so now let's just

find minimum USD and replace that with

all caps as well with this interaction

we know that this variable is a constant

variable and it's much cheaper to read

from now if we go ahead compile this and

redeploy in our fund Rec contract even

though this is a view function remember

view functions do have gas costs when

when called by a contract as a constant

variable we can see the execution cost

of this variable

21,45 gas so let's put a little note

right underneath it if we remove the

constant variable we delete this

contract we redeploy collect fundme and

we hit minimum USD again we can now see

how much gas this was cost if it wasn't

a constant variable we can see the gas

cost did indeed go up now on chains that

are much cheaper this gas difference

probably won't make that much of a

difference but on more expensive chains

like ethereum this is going to make a

big difference for example on ethereum

we can actually see current gas prices

on ethereum here we can see the current

gas price of ethereum is about 141 gay

so we'll go to our converter way to way

we'll copy the way price times this

we'll get the gas price of calling our

minimum USD which is this number here

which if we put back in our ethereum

unit converter we can see cost this much

gas and if we times that by the

approximate current price of ethereum

which is around

$3,000 calling minimum USD as a constant

is going to cost $9 calling this that at

a non-constant is going to cost almost

an entire dollar more you you can see

how all these little gas optimization

tricks are going to make your life a lot

better so let's keep this constant

keyword in here we'll learn more about

constant and storage in later sections

of this course now as you're just

getting started with this course and

with solidity do not struggle and do not

worry about making your contracts as gas

efficient as possible in the beginning

and especially right now just write your

contracts as best as you can once you

get really good at gas and once you get

much later on in the course and much

more advanced with solidity then you can

start going back and working on gas

optimizations but do not let gas

optimizations hold you back or if you

start stressing over it just let it go

don't worry about it and just write your

code as best you can so long story short

do not stress about gas optimizations

right now now another variable we only

set one time is going to be our owner

variable owner equals message. sender we

set this this one time in the

Constructor variables that we set one

time but outside of the same line that

they're declared and we set them for

example in the Constructor we can Mark

as a mutable typically a good convention

for marking immutable variables is going

to be doing I underscore so that we know

that these are immutable variables they

have very similar gas savings to the

constant keyword owner of course is a

variable that we can't set on the line

here because inside the global scope

there's no function going on how over

inside functions because inside the

global scope there's going to be no

message. sender there's only going to be

a message. sender when we're inside of a

function so inside here we might say I

owner equals mesh. sender and then of

course we'll scroll down and we'll

change this require only owner now

equals I owner now if we compile that

and deploy it we can see how much gas we

can see how much gas calling I owner is

going to be by with the IM muteness we

get

2158 which we'll go ahead and copy for

now and we'll put right here we'll say

immutable now if we remove the immutable

keyword let's close this

redeploy now if we scroll down to I

owner scroll up the logs we go down to

the call scroll down we see the

execution cost was much more so we'll do

double backslash paste that in here gas

we not on immutable so you want to keep

some of these tricks in mind when it

comes to storing variables the reason

that these two save gas is because

instead of storing these variables

inside of a storage slot we actually

store them directly into the bite code

of the contract and like I said don't

worry too much about that for now later

on in the course we'll teach you more

about storage and a lot of this

low-level stuff that comes with these

contracts but for now just know that

these exist and they're nice gas Savers

if you're only setting your VAR Ables

once all right great so we've just made

our contract a little bit more gas

efficient little gas efficiency

improvements are going to be Concepts I

sprinkle throughout this course and when

we get to the more advanced section I'm

going to break down exactly what's going

on and why all these gas efficiencies

exist and what's going on behind the

scenes for these gas efficiencies to

occur it's a little bit in the weeds

which is why I'm going to gloss over it

right now so if it's confusing don't

worry I wouldn't let these gas

efficiencies be the thing that's slow

you down awesome so we have these two

gas optimizations how else can we make

this contract a little bit more gas

efficient well one of the ways we can

make this more gas efficient is by

updating our requires right now with our

requir statement we actually have to

store this sender is not an owner as a

string array every single one of these

characters in this error log needs to

get stored individually this the string

may not seem very big but it's a lot

bigger than the alternative with what we

can do as of 0.8.4 solidity you can now

actually do custom errors for our

reverts we declare them at the top and

then use ifs instead of require and then

just add our revert statements this ends

up saving a lot of gas since we just

call the error code as opposed to

calling the entire string associated

with the error so for example with our

require down here and with actually with

all of our requires what we could do is

instead of having this require we could

create custom error so at the top what

we could do is we could say

error not

owner and you'll notice that this is

actually outside of the contract here

now what we can do is we can take this

eror not owner scroll down into our only

owner instead of doing a require we'll

do an if statement we'll say if message.

sender is not I

owner then we're going to go ahead and

reverse

with a not owner error this ends up

saving us a lot of gas since we don't

have to store and emit this long string

here now in a lot of code today you'll

still see require a lot of places

because these these custom errors are

pretty new in solidity so you'll want to

get used to writing it both ways I

wouldn't be surprised if in the future

the Syntax for some of these errors

looks like this so that it's more

readable but for now if you want to do a

more gas efficient way than requires you

can can use something like this we could

update all of our requires here for

these custom errors but for now I'm

going to leave both in just to show you

the differences this revert keyword does

the exact same thing that required does

without the conditional beforehand so

you can actually go ahead and and revert

any transaction or any function call in

the middle of the function

call now let's look at one more way to

improve this contract sometimes people

will try to interact with a contract

that takes ethereum or the native

blockchain token without actually going

going through the required function

calls that that are needed for example

on a JavaScript evm here I could

actually try to send this contract money

without calling the fund function

however if I were to do that what would

happen would our fund function get

triggered no it wouldn't get triggered

we wouldn't keep track of that fun we

wouldn't have that person's information

updated in this contract so if later on

we want to give rewards or something we

wouldn't know about those funders and

this wouldn't be great cuz people would

send our contract money without us ever

knowing and we wouldn't be able to give

them any credit or anything additionally

maybe they called the wrong function by

accident and they they weren't using

metamask and they weren't using a tool

to tell them hey this transaction is

likely going to fail so what can we do

in this case what happens if someone

sends this

contract eth without calling the fund

function right now if we were to send

this fundme contract eth it would just

go to the contract contract right and

this contract just wouldn't keep track

of those people but there's actually a

way for when people send money to this

contract or people call a function that

doesn't exist for us to still trigger

some code and now there are two special

functions in solidity one is called

receive and one is called the

fallback now in solidity there are

actually a number of special functions

and two of these special functions are

the receive special function and the

fallback special function a contract can

have at most one receive function

declared using the receive external

payable without the function keyword

this function cannot have arguments

cannot return anything and must have

external visibility and a payable State

mutability what does that actually mean

and or look like well let's create a

separate contract to go ahead and play

with this so in here we're going to

create a new file called fallback

example. soul and in here we're going to

add our basic pieces SPX license

identifier MIT pragma

solidity

0.8.7 and we'll do contract fallback

example like so feel free to pause the

video to catch up to this point once we

create our fallback contract let's

create a variable to go ahead and try to

test this function we'll create a un 256

public result variable and let's create

this receive function so we'll say

receive it's going to be an external

payable

function we don't add the function

keyword for receive since solidity knows

that receive is a special function

whenever we send ethereum or make a

transaction to this contract now as long

as there's no data associated with the

transaction this receive function will

get triggered what we can do in here now

is we can say result equals 1 so let's

go ahead and test this out on the

JavaScript virtual machine we compile

this so we're going to go ahead and

compile this we'll go deploy it on the

JavaScript virtual machine we're going

to deploy our fallback example and we're

going to see what result is initialized

to since we haven't set anything for

result result of course is initialized

to zero but what if we were to send this

contract some ethereum well receive

would go ahead and be triggered here we

can actually send this contract some

ethereum directly by working with this

low-level interactions bit here don't

worry about what call data means for now

just know that this area down here is a

way we can send and work with different

functions and we can add parameters to

this transaction by going up here and

adjusting the variables up here if we

keep call data blank it'll be the same

as if we were in metamask and just

hitting send and then choosing this

contract address again we can't actually

use metamask since this is a virtual

machine and not one of the networks that

we're working with so if I do for

example I change this value to one way

and I keep everything blank and I go

ahead and hit this transaction button

which again is going to be the same as

hitting this send button but only

sending one way what do you think will

happen well let's try it we can see in

the log area that we did indeed send a

transaction and if you look at the

description here you can even see it

says from so and so to fallback example.

receive it looks like it called our

receive function which should have

updated our result to one so if we hit

result now we can indeed see that result

has been updated to the value of one

well let's go ahead and delete this

let's deploy this contract again and

this time let's have value be zero does

receive get trigger this time so let's

pull this down let's hit transact let's

leave the call data blank we'll leave

value at zero so this will be the same

as if we had sent zero ethereum to this

contract let's hit

transact looks like that went through do

you think result is going to be one or

zero you thought one you were correct a

receive function gets triggered anytime

we send a transaction to this contract

now and we don't specify a function and

we keep the call data blank when working

with any other contract like fundme for

example when we call one of these

functions we're actually just Po in this

call data bit with certain data that

points to one of these functions up here

if we send a transaction and we add data

to it we could actually call one of

these functions now let's try this again

let's delete the contract again we'll

redeploy open this up result is

currently zero receive like I said only

is triggered if our call data to it is

blank now this time if I add some call

data to this transaction you think

receive will be triggered this time if

we hit transact and remix we actually

get a popup saying fallback function is

not defined this is because whenever

data is sent with a transaction solidity

says oh well since you're sending data

you're not looking for receive you're

looking for some function so let me look

for that function for you hm I don't see

any function that matches the 0x0 0 so

I'm going to look for your fallback

Function Remix is smart enough to know

that we don't have a fallback function

the second special function in solidity

is called the fallback function this is

very similar to the receive function

except for the fact that it can work

even when data is sent along with

transaction so our fallback will look

something like this

fallback

external

payable result equals 2 fallback is

another one of these functions where

we're not going to put the function

selector because solidity is expecting

this actually you're already familiar

with one other special function if we go

back to our funme our Constructor for

example is another type of special

function there's no function key keyword

solidity knows that this Constructor is

immediately called when we deploy this

contract so now we have our fallback

function let's go ahead and compile this

let's delete our old

contract let's go ahead and deploy this

new contract let's click here we hit

result we do indeed see it's set to zero

now if I add this 0x00 0 and I send this

and I hit transact this is equivalent to

calling our contract here without a

valid function so our contract goes hm I

don't recognize what you're trying to

tell me here I'm going to refer you to

our fallback now if we hit result we see

that it's been updated to two if we take

this away solidity will go hm it looks

like you're trying to send some ethereum

or call this contract without specifying

what you want to do well I have a

receive function so I'm just going to go

ahead and forward you to that so if we

call transact we hit result we see it

updates back to one add some data hit

transact we see it updates to two no

data updates to one solidity by

example.org has a wonderful little chart

that we can use to figure out whether

not receive is going to get triggered or

fallback is going to get triggered if it

is empty and there's a receive function

it'll call the receive function if it is

data and there's no receive function

it'll just go to the fallback function

and if there's no fallback function it

might just it might error out so this is

a lot of really fantastic information

here how can we apply this to our fundme

contract here well what we can do now in

our fundme is we can add these fallback

and receive functions just in case

somebody actually sends this contract

money instead of calling the fund

function correctly so what we can do is

let's add a receive function so if

somebody accidentally sends it money we

can still process the transaction we'll

say receive is going to be external

payable and we'll just have the receive

function call fund and we'll do the same

thing with our fall

function we'll have fallback external

payable we'll just have it automatically

call fund now if somebody accidentally

sends this money without calling our

fund function it'll still automatically

route them over to the fund function

this means too that if somebody doesn't

send us enough funding it'll that

transaction will still get reverted so

let's go ahead now and let's switch to

rink B to test this on a real test net

I'm on rink be and my metamask let's

switch over to injected web 3 and we'll

scroll down we'll choose our fundme

contract and we'll go ahead and deploy

this menam mask pops up I'm going to go

ahead and confirm the transaction and we

see our fundme contract here right now

we can see the own we can see I'm the

owner we can see minimum USD and we can

see of course that it's a blank contract

and there's nothing funded in here if we

copy the address and then go to Rinky

ether scan

paste the address in we can see that

there's no ether in here and the only

transaction associated with this has

been the contract creation we saw what

happened before when we hit the fund

function our contract was updated with a

new balance and that funer was added to

our array let's see what happens now if

we just directly send this contract

money without calling the fund function

here if we did this right our receive

function should pick it up and kick the

transaction over to fund so let's copy

this address we'll go to our

metamask we'll hit send paste the

address in here we'll do 0.02 eth again

because this should be more than the

minimum amount in USD we'll hit next

I'll go ahead and confirm this and after

a slight delay if we did this right well

we should see this transaction having

called the fund function here now that

our transaction has gone through and

after a brief delay and waiting for

ether scan to update we do indeed see

that our balance has updated to

0.02 which of course this makes sense

and we see in the transactions list here

we see that this actually went through

as a as a transfer instead of what's

calling the fund function let's go ahead

and remix and see if our funders was

updated it looks like it was at the

zeroth position of funders we have our

address and if we take our address and

pop it into address to amount funded we

can see exactly how much we had funded

this means that since we added this

receive function in here we

automatically had to call our fund

function up here so awesome work we were

able to add a receive function to help

people who accidentally call the wrong

function or accidentally send this

contract money instead of correctly

calling the fund function now if they

had directly called the fund function it

would have cost them a little bit less

gas but at least this time they're going

to get credit and added to to our

funders array for having sent our

funding contract

money we've even learned some Advanced

sections of solidity and this is going

to be the last time that we start our

projects in remix we're going to be

moving over to a code editor now where

we can get even more advanced with our

solidity and our setups for the most

part you've gone over the vast majority

of solidity Basics there are a number of

things that we still haven't learned yet

and the reason we haven't gone into them

is because they get more advanced and

understanding the real use doesn't

really make too much sense until a

little bit later some of the things that

we're going to go over are enims events

try catch function selectors ABI

encoding hashing and then U slash and

then u/ assembly however if you've

gotten this far you probably can read

most solidity code and understand what's

going on which is absolutely fantastic

so you should give yourself a huge round

of applause for getting this far in

doing this let's do a quick summary of

this more advanced section and make sure

we understand what we learned in Sol

there are a couple special functions

some of them are receive fallback and

Constructor these functions don't need

to have the function keyword and instead

can just be called like so receive and

fallback are two very special functions

if data is sent with a transaction and

no function was specified the

transaction will default to the fallback

function if that fallback function

exists if data is empty and there's a

receive function it'll call the receive

function there are a couple of keywords

that can help us save gas in the long

run some of those keywords are going to

be constant and immutable constant and

immutable are for variables that can

only be declared and updated once once

we say minimum USD is 50 * 1 E18 this

minimum USD can never be changed again

and this helps us save gas IM mutable

can also save gas similar to constant

however immutable variables can be

declared one time in the Constructor

once an immutable variable is declared

it can't be changed later on in fact if

we even tried to update an immutable

variable or a constant variable and we

compiled a compiler would give us an

error saying can't write to immutable

here or if we tried to change a constant

variable our compiler would say hey you

can't assign to a constant variable

sorry in remix if we want to send ether

to a contract that's on the JavaScript

virtual machine we can deploy that

contract and then in the contract we can

just hit the transact button without any

call data and update the value that we

send with the transaction if call data

is blank it'll trigger a receive

function if it exists but if there's

data that doesn't specify any of the

other functions it'll trigger the

fallback function

all right my code's done time to ship it

free box to you dog water zero earn zpr

in the age of AI debugging and getting

into software engineering has never been

easier here the exact six steps you need

to take to unblock yourself from any

software engineering area you'll ever

get number one Tinker try to pinpoint

your air you can usually use an AI buddy

to help you out here pinpointing your

air will potentially solve your problem

before even going to an AI and allow you

to craft a better question to an AI once

You' pinpointed the issue you can move

to step two which is ask your AI you can

use chat gbt find Bing's AI or if you

want to get wrong answers Google's

barred there's six principles to prompt

engineering so that you can get the best

out of your AI write clear and Specific

Instructions give as much context as

possible use delimiters to clearly

indicate distinct parts of the input and

especially look out for something called

hallucinations hallucinations are when

your AI gives you an output that it

thinks is right but it's completely

wrong for example if I write about

writing solidity and variant tests in

Foundry disgraces Us by saying we have

to mpm install it from open Zeppelin

these can be tough to spot but once you

try it out you'll see it doesn't work

and finally you want to understand the

limitations of the AI you're working

with and iterate constantly large

learning language models are trained on

human conversations so you can interact

with them as if you're having a

conversation but it's important to know

the limitations of these AIS as most AIS

have a limit on how many tokens or words

they can keep in context at one time AI

is trained off human language so if

you're good at asking other humans

questions you'll probably be good at

asking robots questions too asking

questions is a skill so keep practicing

I've got a link in the description to

learn. deeplearning.ai which is a free

course to help software Engineers be

better prompt Engineers now when the AIS

can't help you you'll have to go back to

the old standbys actually doing work

yourself and one of the first pieces of

work is reading the documentation you

probably should have done this already

however we can still use chat gbt cuz a

strategy that I constantly use is I'll

copy paste sections of the documentation

at chpts context and say some like the

above are the docs for Tool X based on

those docs how do I do why so Google

might be crying because chat PT is

eating its lunch but Google still has

what AI doesn't have the entire internet

previously anytime I ran into an issue I

prayed someone else to run into it

before I made a post on it so I could

Google search that exact issue there's a

new tool called fine that combines web

search with AI as it does a web search

and it crawls through all the data of

the sites reads them all and then gives

you an answer based off of what it reads

five asking a forum sometimes the

information just isn't out there and we

need to ask human beings we always want

to ask our question on a webbed index

Forum like stack exchange stack Overflow

pirana or Reddit this way webcrawlers

and more likely AIS can scrape the data

from these sites and learn from us that

way the next time we have this question

we can get our answers quickly asking on

Discord and Twitter are because your

knowledge will get lost to the

unsearchable hellhole of conversations

that Discord is and web crawlers don't

index them the super secret alpha is to

ask a question on stack exchange and

then post your stack exchange link to

Discord you should 100% always ask your

questions and format them with markdown

and if you're not sure how to do

markdown you can ask chat to to help you

format your questions and markdown ask

on the support GitHub or forum is the

tool you're working on open source

awesome ask a well formatted question on

their git page not open source never use

that tool again this is how we improve

our tools by creating issues engaging

with each other and even taking on

issues and contributing to the open

source code and then finally iterate do

all these same steps over again and as

always keep hopping through the code and

until next time stay riveting my fellow

blockchain ear

[Music]

all right fantastic so now we know a

little bit more about the different

tools and techniques we can use when we

do in fact get stuck we can use

something like chat TBT forums to ask

questions we obviously want to Google

search and especially for this course

you definitely want to make sure you use

the discussions Channel but I wanted to

give you some very specific tips about

working with this course number one

limit your self triaging to 15 or 20

minutes for example if we're trying to

compile our price converter doou and

maybe we forgot to add the address in

here right and we're going ahead and

compile and we're getting this error

this is exactly one argument expected

for explicit type conversion now this

should be pretty obvious what the error

is hey it's expecting one argument and

we obviously just removed that argument

but maybe you're having a really hard

time and you're trying all this

different stuff and you can't seem to

figure it out limit yourself to 15 or 20

minutes we do not want to be messing

around for so long that we can't figure

something out right something like this

would be very easy for us to compile

copy this error go to chat gbt and say

something like hey I'm getting an error

compiling my solidity here is the error

do three back ticks paste it in here

like that three back ticks is markdown

and like we said in the video we want to

use delimiters to clearly identify what

is Code versus what is not oops and I

hit and I hit enter whoops the daisy

we're actually going toit stop

generating and we're going to copy paste

the question again now we're going to

say here is my solidity it's wrong then

we'll copy the solidity

line once again three back ticks we'll

say solidity here we'll paste it in

three back ticks to end it hit enter and

it'll probably give us the answer here

and sure enough the error message

suggests that you need to provide an

address when using explicit type

conversion so we go ah okay whoops we

need to actually add an address in here

it gives us an example and we can go

back to our code and you know paste that

address in here and be good to go so

limit self triage to 15 20 minutes

that's going to be the first tip number

two don't be afraid to ask AI but don't

skip learning the purpose of this course

is for you to be able to learn

everything here AI is going to get

things wrong and it's only the people

who actually have learned what's going

on under the hood who are going to be

able to call out when AI gets something

wrong when AI gets something wrong it

does something called hallucinate and we

talked a little bit about that in that

AI video we just watched so

hallucinations are when the AI makes

something up that it thinks is right but

it's completely wrong and that's

something we absolutely need to watch

out for when we're coding and when we're

learning a perfect example of this is

with Foundry which is a tool we're about

to learn very soon in order for us to

install Foundry we actually need to run

this Command right getf founder. sh it's

the first thing that it tells us to do

at the time of recording chat gbt has

not been trained on The Foundry tool so

if I ask it a question like I'd like to

initialize a Foundry project with

solidity can you show me how to do that

and we'll let enter so the first

sentence out the gate is wrong it's not

aware of Foundry so it tried to guess

what Foundry was and it got it wrong it

is not a CR space framework for building

blockchains at all and it is directly

related to solidity so it's really

important that we use AI to augment our

learning but we don't skip over the

learning with AI it's really good to

bounce questions good ideas off of but

in order for us to be even able to

recognize when Foundry is hallucinating

and making stuff up we need to have that

knowledge ourself step three of course

use the forms web3 education. deev will

have a place for you to ask questions

but in the meantime definitely be sure

to use The Foundry full course

discussions use this to your advantage

and use this to help other people out

who have questions this is a community

project we're all going to be helping

each other out learning number three

Google the exact error if AI doesn't

know the forms aren't know Google the

exact error maybe somebody else has come

across this error previously asked the

question online and you can just Google

it and then of course post your question

in stack exchange or piranha and like we

said in that AI video you want to use

markdown and format your questions as

best as possible so if you're unfamiliar

with how to use markdown if you're

unfamiliar with how to format your

questions again please be sure to ask

chat GPT or some other AI how to best

format your question you can even simply

say ask chat GPT could you give me an

example of a well formatted stack

Overflow question with Cod or code and

it'll actually give us a really good

formatted question so it gives us the

question it formats the code for us it's

using this with the three back ticks

that I showed you in order to get this

code block here it's using three

backticks and it's being very verbose in

giving all the details of the question

so be sure to ask questions like chbt

awesome again let's say we're in here

compile get this error exactly when

argument expected for explicit type

conversion if we copy this error go to

Google we paste just the error in we'll

remove this our specific code looks like

the first thing we get in Google is

actually contract inheritance and we can

see that this is actually exactly the

error that we're getting it looks like

this does actually explain the answer

but it's a little bit confusing to

understand here so maybe you would copy

paste this into chat gpts context right

there's a lot of creative ways you can

approach debugging some of your issues

obviously when you're out in the wild

and you're actually building things

yourself obviously the education site

and the discussions channel of the giup

repo the people in these aren't going to

have context for the new creative thing

that you're working on so I want you to

get used to doing that methodology that

we're teaching here right asking your AI

buddy if your AI buddy doesn't know

Googling asking questions on stack

exchange ethereum asking questions on

piranha piran is arguably better because

you're asking your questions in a

decentralized location as opposed to a

centralized server but I definitely want

you to practice asking questions and go

to piran go to stack exchange make

accounts for these so that when you do

run into an issue because you will

you'll know where to post them high

encourage you to pause and post a

question on one of these forms right now

now just so that you get used to it just

so that you get out of your shell and

you're going to suck at asking questions

in the beginning and that's okay you

will get better at asking questions as

you continue with this course asking

good questions is a skill in itself and

if you learn how to ask very good

questions that's the secret sauce to

being amazing at AI prompting as well

now the final step in all of this is

actually going to be posting an issue on

GitHub SLG a surprisingly incred

important part of being a software

engineer and being a developer in web 3

is interacting with the community the

vast majority of these tools that we're

working with are going to be something

called open source meaning that the code

associated with them is actually

available for anybody to view this tool

Foundry that we're going to be working

with is one such example and if you see

it has this issues tab where there's

just a ton of issues people are posting

while using this tool this is how code

is able to be improved and move forward

all this code is public for people to

use and work with and if there's a

question that isn't answered you can

post here and tell the developers of

this tool hey I'm running into an issue

maybe we should make a project

Improvement I would say be very

respectful with the way that you make

issues you definitely want to do some

searching on issues to make sure that

nobody else has asked the question that

you're working with and be to sure to

use these other resources first like

panha like stack exchange but in the

future once you leave this court it's

going to be incredibly important for you

to participate in the ecosystem by

making issues by making poll requests

and actually improving some of the tools

that we're going to be working with

yourself even ethereum has a GitHub and

if there's any improvements that you

want to make you can add an EIP to

actually improve ethereum we'll talk

about EIP some more later you can

improve some of the clients that

ethereum runs so interacting with each

other is incredibly important and in

fact if you don't have a GitHub we are

going to get you set up with GitHub

right now because GitHub is the platform

that most developers use to share code

and write code and interact with code in

between each other so if you don't have

a GitHub let's sign up right now and

we're going to use the GitHub to create

our own portfolios of all the different

cool coding projects that we've created

this way when you go to apply for a job

you can say hey go look at my GitHub

I've got all these really cool projects

so we're going to make you a GitHub

right now if you don't have an email

you're going to need an email I made a

burner account just for this video and

I'm also going to walk you through

formatting a question and I know I'm

belaboring the point here but I really

really want to stress the importance of

formatting these questions really well

so we're actually going to show a clip

from my past video so we're going to be

using the full blockchain cility course

JS but again for this video just be sure

to use the GitHub repo associated with

this course and not that other old

GitHub repo all right let's watch this

video in fact if you haven't already

let's sign up for for GitHub right now

and let me walk you through formatting

one of these questions because the

better you format your questions the

better chance you have of actually

getting the answer and remember when

asking questions on these forums when

asking questions in these discussion

communities people answer these

questions out of the goodness of their

heart right so if you don't get a

response there's a chance that maybe

nobody knows maybe it's your question

isn't formatted very well and Etc so

we're going to learn how to ask really

good questions here and if you're new to

blockchain do not skip this section okay

this is going to be that piece that's

going to give you the superpower to

unblock yourself from any coding issue

you run into so don't skip this part be

sure to follow along okay so if you

don't have a GitHub already you do need

an email to get started so I'm going to

go ahead and sign in I made a burner

account just for this video so what

we're going to do we're going to go

ahead and sign up GitHub enter your

email and we hit create account they're

going to send us an email so we're going

to come back to our email going to get

our launch code here paste it

in answer a little bit of

information we're going to choose the

free

version and fantastic we've now created

a GitHub

profile awesome so now we've created a

GitHub so I'm actually using a GitHub

that I used in my last course so that's

why I have all these repositories over

here now in order to create a new

discussion disc Over The Foundry full

course f23 let's go over to the

discussions tab we'll hit new discussion

and we'll hit General and I'll say

something like test discussion be like

feel free to say hello here start

discussion now I'm going to show you a

question that's formatted poorly and I

want you to never ever ever ask a

question like this and if you see

somebody ask a question like this please

help them format their question

correctly hey why my code not be good

and then let's just have it be issue

like this right what's wrong wrong with

this okay well why my code not be good

obviously isn't clear what's going on

the code isn't formatted well and even

an AI would have a hard time answering

this so let's fix this to be a little

bit better as we know we want to copy

the exact error we're getting so we'll

say We'll copy the error we'll go back

we'll say I am receiving this error

we'll do the three little back ticks

paste our error right in here like that

actually let's be even more exposit I'm

receiving this error while compiling

here's my code re betic we'll put

solidity here copy the whole line that

is erroring paste it in here and someone

help me figure out what the issue is

right and you see how this is much much

better right we have these two blocks

that pop up because we did the back

ticks and the secret is that this is

going to get you a much better answer

from an AI as well right if we edit this

we can copy the whole thing in markdown

go over to chat jbt paste it in zoom out

a little bit and we're going to get it

actually an answer hey you're receiving

this air because you're trying to create

an instance of aggregator V in phas

without providing the necessary argument

blah blah blah oh and it actually gives

an updated version of that but it helps

us out here so ask format your questions

correctly you will get better answers

from both AIS and humans and I know I'm

spending a long time on this but I

really really need you to understand

that the secret to prompt engineering is

actually just being able to ask better

formatted questions with human beings

and it's better for interacting with

human beings as well now the other thing

that I did really well here was I only

posted the relevant code to the error

that I was getting what we see a lot of

people do is they just copy paste their

entire code base into here this is not

very helpful as it's going to make

somebody who wants to help you their job

a lot harder if they have to read your

entire code base right we reply here

this is so much more reading for them to

do it's going to take them a lot longer

and they might not actually read it and

we didn't actually highlight this with

the back ticks and it goes the same

thing with AI if you give your AI too

much text it can't read all of the text

because again some of these AIS have

limitations in how much text they can

read so it's the exact same thing with

working with human beings so feel free

to take some time to either in chat BT

or whatever AI you're using or in this

test discussion forum to post some well

formatted question questions and

remember you can use AI to help you get

those formatted questions in markdown be

sure to ask chat WT to give you the

output in markdown so if you haven't

worked with markdown before that's okay

you'll learn as you go along but one of

the biggest differences especially when

working with markdown that's going to

make your code so much more readable and

I 100% need you to always do this

whenever you ask questions is you see

how this got like some syntax

highlighting in this above question well

if we go click edit again we can

actually see why up here we did those

three back ticks and then we typed the

word solidity when you do these three

back ticks in your questions if you type

the word or you type the language next

to the first three back ticks it'll

actually add some formatting to make it

more readable so if we scroll down to

this poorly formatted question you can

see that this is just all white and like

impossible to read it would be at least

slightly better if we hit edit and next

to these three back ticks we wrote

solidity if this like Java code or

python code we could write python or

Java or whatever but since this is

solidity we'll write

solidity I'll hit

update and you can see that it is

substantially nicer and it is much more

readable now so even though this is

still a bad question obviously because

we just copy pasted all of our code it's

at least much more readable so anytime

you do a code block like this of any of

your code absolutely 100% be sure to do

the three back ticks and then the

language of the block of code so just

remember this there are no bad questions

but there are poorly formatted questions

make your questions well formatted for

both human beings and for AI and then

most importantly be sure to join these

forums and like I've said 100 times

interact with these people interact and

help and give back the more people that

use and are good at the tool that you're

working with the more likely that

they're going to help you sometime in

the future and this is how I've met so

many people in the industry is just

giving back in interacting with other

people so whenever you ask a question

especially in the beginning cuz in the

beginning you're going to have more

questions than not be sure to at least

try to go back and answer a question

think of it as question and answer debt

every time you answer a question make a

little mental note and say ah in the

future I need to at least try to answer

one of somebody else's questions this is

how we grow and move so much

faster now this next piece that I'm

going to show you is outside of this

course but it's a resource that I wanted

to show you in case after this course is

done you want more resources to learn

about ethereum and learn about the EVN

it's with my good friend Austin who's

going to show you speedrun ethereum and

definitely something you might want to

check out after taking this course

what's up I'm Austin Griffith happy bow

tie Friday I want to show you the best

way to get started building on ethereum

is speedrun ethereum.org

[Music]

you'll build a decentralized staking app

you'll learn that the superpower of

ethereum is allowing you the Builder to

create a simple set of rules where an

adversarial group of people can

coordinate financially you'll build a

token vendor you'll build a dice game

and you'll learn about Randomness on

chain and where it works and where it

doesn't and what you can do about that

you learn about a DEX and what a hyper

structure is and how people can use

liquidity to swap you'll learn about

State Channel and scalability and sign

messages and multisig wallets and

account abstraction and SVG nfts lots of

fun stuff along the way like I said not

just the how but the why go to speedrun

ethereum.org and get started today uh

it'll have you do a quick video uh and

then it says to use scaffold eth to

start tinkering I want to show you how

to do that first of all all this stuff

is open source uh it's all ungated and

open source just get in and get get in

get learning okay but this scaffold e

thing uh scaffold e is a great way to

Tinker with solidity and kind of get

your your your bearings right so let me

show scaffold 2 just for a second if we

zoom in uh I've already kind of uh gone

through the whole readme and installed

everything I want to show this right

here here's a smart contract and I have

my front end that's uh Auto adapting to

the smart contract and so uh when in

speedrun ethereum it tells you to Tinker

with each one of these Concepts let's

just go look at mappings or strs or

modifiers let's just go look at get a

mapping and let's grab a mapping right

and let's copy and paste it right into

our smart contract so something called

my map I don't even know what it is

right and then we yarn deploy and we'll

see that my map show up over here and

this is kind of the feedback loop I want

you to get into where you can grab some

stuff from solidity by example paste it

into your smart contract deploy it

locally and then Tinker with it there's

my my map let's see what vitalic bance

is in my map

it's zero oh okay so check out speedrun

ethereum check out scaffold e get

started building cool things on ethereum

today happy bowai Friday hearts hearts

hearts see you

now the reason I especially wanted to

show you all of these debugging things

right now is because we are about to

move off of remix remix has been this

phenomenal IDE or this phenomenal

integrated development environment that

allows us to quickly try things and

quickly deploy things but we're actually

going to move off of remix to a more

professional setup and we're going to be

using a modern set of tools that most of

the rest of the development community

also works with and I'm going to tell

you this right now often installing

these new tools and often just getting

your local development environment set

up not using remix or not using what's

called a cloud IDE can often be the

actually most difficult step in this

whole process so I want you to be

absolutely Vigilant in using all of the

resources that I just showed you using

the chat using chat GPT using piranha

using stack Exchange eth using web3

education. once we get this up and live

be sure to use these tools and don't let

installing these slow you down because

in my mind installing these can be the

hardest part of this whole course and

it's okay things might not work the

first time and that's okay just be sure

to ask questions and be very specific

with the errors that you're seeing and

installing these things that's what

we're going to learn how to do right now

so remix is a phenomenal tool but now

we're going to move over to this more

professional setup called called Foundry

Foundry is one of the most popular smart

contract development Frameworks similar

to hardhead or brownie if you're

familiar with those and it's known

specifically for its speed Foundry is

easily the fastest to work with smart

contract development framework one of

the unique aspects about Foundry is that

whereas hard hat is Javascript based

brownie is python based Foundry is

completely solidity based so we don't

have to learn any other programming

languages other than solidity to work

with Foundry and similar to everything

that we we've been doing so far all of

the code for all of our Foundry products

are going to be in the GitHub repo

associated with this course however the

documentation for Foundry I think is

also phenomenal so be sure to use this

as you code along and something very

interesting that I really love to do

most of these pages are pretty small so

even if your AI isn't trained off of

Foundry which as a recording it's not

what we can do is something called

context injection when we have issues so

we can copy the entire page of Doc

mentation we can say I'd like to start

I'd like to install Foundry here are the

documentations for installation how can

I do it do the three back ticks paste

the whole thing in there and by giving

our AIS the documentation for working

with Foundry it's actually going to give

us outputs to install Foundry so this is

a methodology you'll see me use from

time to time this context injection you

can find more

in the GitHub repo once again associated

with this course on installation and

setup Mac OS and this should be Linux

and then we have some Windows setup

stuff down here we're going to go over

how to set up all the important things

for this course so be sure to use this

as a reference now a great question you

might be asking is well what's even the

purpose of Foundry why do we need to use

this other tool remix is working great

well in remix you notice that we did a

lot of stuff manually like I came in

here I had to go to compile maybe I

wanted to test something out I would go

deploy it uh I got a put a price feed in

here a price feed in here deploy okay

does the get version work Uh something's

wrong with my get version okay my o i

owner works okay minimum USD works oh

crap I got to go make some little change

here you know maybe I want get version

to actually return you know 7 + 2 or 7 +

1 now I got to go you know delete this I

got to go redeploy I got to go click

this I got to go down I got to click and

then if I have a hundred things that I

change testing all of this is going to

take a really long time and anytime you

do something anytime us as human beings

changes our code in some way there's a

chance that we break something and

remember these smart contracts are

immutable so if we break something if we

mess something up that's really bad

because that mess up will be permanent

on the blockchain so we want a framework

that helps us deploy our smart contracts

test our smart contracts and interact

with them in a much more programmatic

way rather than we having to manually

click around right if I changed 10

functions and I wanted to test the work

I would have to go click 10 buttons

that's ridiculous in Foundry we can do

all of that in one command or one button

so that's why we're going to be using

Foundry here and I'm so excited for you

to be using this Foundry tool because

like I said it's the fastest smart

contract development framework out there

right now but additionally it's also the

framework of choice for smart contract

security engineers and Auditors and I

expect more and more projects in the

future to be built in Foundry so

incredibly excited for you here now for

the rest of the course I'm going to be

we're using a code editor called Visual

Studio code this is one of the most

powerful code editors on the planet and

if you've already got it set up feel

free to go ahead and skip this part

you'll often hear people refer to this

as VSS code or Visual Studio code or

just Visual Studio however it's

important to not that Visual Studio code

this is different than Visual Studio

which you might see look like this so

visual studio code is what you want not

Visual Studio Visual Studio is a

different application make sure you're

on Visual Studio code now if you choose

so and you're a total Hardo you can

absolutely work just with your terminal

or just with Powershell or just with

whatever coding environment that you

want like atom or Sublime however for us

we're going to be working with Visual

Studio code and I'm going to be going

through setting up visual studio code

the way that I like to set it up you can

absolutely set it up whatever way that

you feel comfortable now we're going to

go through three different installation

processes and pick the one that's most

appropriate for you the first one is

going to be for mac and Linux users the

second one is going to be for Windows

users and then our third one is going to

be a last ditch effort if for whatever

reason you can't get Windows or Linux or

the Mac instructions to work we're going

to use a git pod installation now I

highly highly recommend that you try to

get everything working locally without

using git pod however if for whatever

reason you can't get those installation

pieces to work we will have git pod

instructions for all of the repos that

we work with here but to get started

we'll start with the mac and Linux

installation

instructions the first thing you're

going to want to do is download the Mac

or if you're working with Linux download

the Linux installation of Visual Studio

code once you have it installed it'll

look a little something like this and if

it's a fresh installation it'll even

give you some tips and tools to actually

get started if you've never worked with

Visual Studio code before I highly

recommend going through any get started

or getting instructions tips that come

with opening Visual Studio code

additionally we have a visual studio

code crash course in the GitHub repo

associated with this course now one of

the awesome things about Visual Studio

code is it has this thing called

terminals which are commandline promps

that allow us to run scripts basically

it's where we're going to be running all

of our code the way we can open up the

terminal is we can go ahead and hit

terminal and select new terminal and

you'll get something like this now you

might have bash or zch or some other

type of shell the type that you have

doesn't really matter because on Mac and

Linux it's going to be Linux based and

like I said sometimes installing this

can be the hardest part of this entire

course so so don't get discouraged and

please use stack overflow stack exchange

ethereum and the GitHub repo to to move

past any issues you run into now if

you're on Mac or Linux you can actually

hit control back tick to actually toggle

your terminal mode this will pull the

terminal up and down for you getting

familiar with keyboard shortcuts will

actually make your life a lot easier cuz

you'll be able to move around Visual

Studio code much more effectively we

have a link to a list of keyboard

shortcuts additionally in the GitHub

repository associated with this section

as we move along I'll give tip on

different keyboard shortcuts that you

can optionally use otherwise you just go

ahead and click as well you can click

the trash can to delete the terminal go

back up terminal new terminal to pop it

back up now the next thing that we're

going to need a little bit later we're

not going to need it for this section

but it's good to install it now is going

to be git we will have links to the

installation instructions in the GitHub

repository installing git on Linux

you're going to use one of these two

commands and on Mac OS if you just type

git on the command line it should go

ahead and prompt you to install it so if

we're back in our command line and we

just type get it should prompt you to go

ahead and install it and if you do g--

version you should get something that

looks like this you can also use a Mac

OS git installer by clicking this link

here and running through the

installation process all right now that

you have git and visual studio code

installed we can continue on to the next

section awesome if you're not planning

on using Windows or git pod feel free to

skip the next two

sections and for this Windows setup

we're going to be learning about a tool

called WSL and to introduce that to us

we have my friend basili who has done

amazing work helping me on some of my

past courses and he's going to be

helping us here today so take it away

this tutorial is going to be useful for

any Windows version from Windows 10 and

above let's get started by installing or

code editor in this case Visual Studio

code so let's type BS code on the

browser and hit

enter s or version for Windows select

the destination and click save and the

installation process is going to be the

same as any other program so let's

select an accept the agreement click

next add code to the pat create a

desktop icon next and

install this shouldn't take a lot and

this is how the editor is going to look

like the first time we install it we can

customize the theme create shortcuts and

sync with another

devices and if you want to go deep into

Visual Studio code well I suggest you to

pause the video for a moment and go

through all these steps one by one now

we could 100% go forward and install the

rest of our Tools in a Windows

environment but basili is actually going

to explain to us that the windows

environment isn't really actually the

best way and the best place to do our

installations Microsoft has definitely

increased their support for developers

in the recent years but when it comes to

Smart contct development there is a

better option to consider using WSL the

windows subsystem for Linux trust me is

a game changer you see a smart contract

development often involves working with

tools and utilities that are commonly

found on Unix based environments while

Windows has come a long way in

accommodating developers there can still

be some challenges when it comes to

ruining certain command line tools and

setting up the right development

environment not mentioning that if you

want your code to run on any machine

using a units based system Mac and Linux

is better for your developer needs here

is where WSL shines by installing a

Linux distribution through WSL you can

access to a full-fledged Unix light

console right on your Windows machine

and don't worry you don't need to be a

hacker or wear a hoodie to make it

happen is actually quite simple so let's

do it for that let's open the windows

terminal this is a pre-installed

application on Windows

11 and so something you can easily

install through the Microsoft store on

Windows 10 just type terminal and here

you are going to have the windows

one so let's install WSL by typing WL

minus minus install hit enter is going

to trigger us a admin operation and

installation is going to start and here

we just have to wait until the process

finishes once the process is done this

will require you to reboot your

operating system system so I'll see you

on a second once rebooted this is going

to automatically open this terminal and

the installation process is going to

proceed now you have to input a new Unix

username for me is going to be chare and

then you have to set up your password

don't worry the password is always

hidden on Linux operating systems and as

this as that we already have a operating

Linux terminal inside our Windows

machine so we can now close this now if

we open a new instance on the Windows

terminal we click here on this drop-

down arrow we can have now this obuntu

shell on which we are going to inst all

the development requirements we are

going to use during the course so the

next step is to make Visual Studio code

compatible with WSL so let's do

that let's go to the extension stab

let's search for remote development and

install all these extensions this is

going to automatically install the

compatibility to connect or Visual

Studio code with WSL and as you can see

over here I have a new econ called open

a remote window if I click here I can

directly connect to WSL however there is

an easy way to do this let's close Vis

Studio code and on the Linux terminal

let's just create a new folder for

example Mader solidity course let's move

to that folder and now let's open Visual

Studio code inside this folder just type

code dot hit enter this is going to

install the latest server for w cell on

Visual Studio code and once this is done

we are going to have a new instance of

Visual Studio code but using WSL let's

just trust the outdors and as you can

see here I'm getting this WSL Ubuntu

Banner over here and and is because I

already connected this with the Linux

instance so you have two options from

now on you can start using just the

windows terminal to execute all the

things we are going to need or you can

use the integrated terminal which comes

with Visual Studio code just go to

terminal new terminal and now we are

going to have a terminal using the exact

same W cell instance so we can start

using PSE sudo commands for example to

the AP update and this is going to work

properly now just take something in

consideration maybe you are going to

develop all your projects on a folder

called development inside your documents

on Windows and you can do so however if

you take a look to the Linux terminal

with ls command as you can see here you

are going to have just access to the

local files and folders inside of the

WSL instance and I highly recommend you

to do that because of course you can do

something like typing the address of

your local development folders and use

the projects from here but the

communication from the WL console and

the local Windows files are actually

quite slow so I prefer just to keep

Simple and use all the folders inside W

cell remember that you have to just

manage simple commands such as LS to

know all the folders on the current

directory and CD to navigate through

them now if you go back to your vs code

and you hit terminal new terminal and

open up a terminal we're going to want

to then install git we're not going to

use git for this lesson however we will

definitely be using it in the future see

if git is installed type g-- version

sometimes Linux will automatically come

with get installed and you'll see

something output like this however if

you are the ones who decided to keep

using po sh

and just Windows instead of WSL don't

forget to go to the official git page

and install it for Windows the process

is as same as we did before pretty

standard just the common sequence of

clicking next and of course please to

read the license agreement and now if

you've made it this far you should be

able to follow along with the mac and

Linux constructions as if you're running

on a Mac and a Linux even though you're

running on a Windows just be sure that

whenever you're in your vs code you take

a look at the bottom left and make sure

you're on WSL yuntu like I said before

if you want to run in Powershell or in a

Windows environment you're more than

free to do so but like I said if you've

made it this far huge congratulations

awesome

work and then finally our last setup is

going to be using a tool called gitpod

starting from lesson five the lesson

that we're on right now ether's JS

simple storage all of our code repos are

going to come with a button in the repo

scroll down they'll come with this open

in git pod button now git pod is a cloud

development environment where you can

actually run your code on a remote

server it's kind of similar to remix IDE

but it allows you to run Visual Studio

code in the browser or connected to

another server this is good because then

you don't have to do any installation on

anything since all the tools that you

want to use are just going to be running

on this remote server this has its

downsides though obviously since you'll

only be able to code if git pod is up

and working for you additionally when it

comes to private Keys you absolutely do

not want to run any code with a private

key that has real money in it on gitpod

why well once again since you're running

your scripts on a remote server those

servers have access to your private keys

but since you've pinky promised that for

this course you're not going to be using

a metamask or a private key with actual

money in it it should be fine the other

downside is that these often cost money

to use and git pod isn't free but it's

an option if you absolutely cannot get

any of the installation working so if

you go ahead and you hit this opening

git pod button you'll get a welcome to

git pod showing up uh we're going to go

ahead and continue with GitHub since

you've signed up for GitHub here you

want to go head and authorize git

pod and it'll go ahead and start

creating this workspace for you and

you'll notice it looks exactly like

Visual Studio code since I opened the

repo up in gitpod it came with all the

code and you can even open this

workspace up in vs code desktop so this

is might be a little bit confusing but

basically you can run off of git pod

using your local Visual Studio code and

if you see G pod here that's how you

know that you're running off of git pod

if you see this popup do you want to

open this workspace in vs code desktop

you can hit open and it'll ask you if

you want to open up visual studio code

which I'm going to go ahead and hit yes

and you'll get something that looks like

this on your Visual Studio code it'll

tell you that it wants to install the

git pod extension and then open that git

pod URL so you can go ahead and install

it reload window and

open and it's going to go ahead and

start connecting to our the git pod

workspace and this is going to be the

same as running git pod in the browser

here or you can also do it manually by

hitting the git pod in the bottom left

and then type in open in vs

code and then you should be able to run

it in your Visual Studio code for now

I'm going to recommend that if you're

using git pod just stay in the browser

just so that you know okay I am running

this on a remote server and just as a

reminder for you that you're not

actually locally developing and

hopefully this will be a trigger to not

actually put any special private keys or

anything like that but you can make

workspaces you can make new folders and

you should be able to run all the

commands on here as if you were running

locally with Visual Studio code to open

up the terminal you hit this little bar

in the top left go to terminal new

terminal or use control Tilda exact same

as Mac OS and Linux keyboard shortcuts

to create a new folder we can change

directory CD do dot

mkdir new folder mkd makes make

directory called new folder and then

we're going to change our directory into

new folder and hit enter and now we're

in that new folder for each section you

can either open up the entire source

code right into gitpod or you can create

a new folder for each section yourself

and start from blank and then you would

just type code period

and you'd be in a brand new

folder and if you're using Windows this

should say WSL or yuntu or something

like that and if you have all that that

means we're ready to go now a quick note

something that you'll see me do a lot

and you can do this as well often times

when my terminal gets really really big

or there's a ton of commands in here

gets a little bit overwhelming for me so

one thing that you can do is you can

type clear and hit enter to clear it or

what you can do is you can hit command K

if you're on a Mac or control K if

you're on a Linux or a Windows and it's

one of my favorite keyboard shortcuts

that I use all the time Additionally the

trash can and the X here are very

different if I go do a couple of enters

here and we're down here if I hit the X

here and then pull my terminal back up

by doing the toggle or by doing terminal

new terminal you'll see all those lines

are still here but if I hit the trash

can and then pull the terminal back up

you you'll see it actually refreshes M

has a special command that prints stuff

out trashing your terminal is basically

deleting whatever is running in it and

the x is just hiding it and it's hitting

control Tilda or toggling our terminal

or whatever command it is on your

environment that's equivalent to hitting

the hide not the trash so if we want to

remove and start a terminal over we hit

the trash can and then we pull it back

up

so after we have that set up the next

thing that we're going to want to

install is actually Foundry itself in

The Foundry book you can find this in

the installation tab or you can go to

get found. sh and it'll have this

command that you can actually just go

ahead and copy Windows users we're going

to teach you how to do it the Linux or

Mac OS way so just stay tuned so we're

going to go ahead and copy this and run

this command again we can go terminal

new terminal and there are also some

shortcuts to do this I'm just going to

go ahead and paste this in here and hit

enter you will need internet access for

this to work because it's actually

downloading Foundry from this website

let me just move this up zoom in a

little bit here and you'll see me do

this a lot in the terminal I'll type

clear a lot to remove anything that's

been coded or output in our terminal

here or you'll also see me do command K

like that which clears the screen when

I'm typing in the terminal you'll see me

hit control w a lot which actually

removes

the most recent block of code you've

written you'll also see me do control U

which deletes the entire line so I'm

going to use command C for copy and

command V for paste a lot for those of

you on Windows and Linux it might be

control C and control V and if you're

unfamiliar you can Google the keyboard

shortcuts for for copying and pasting

for Windows or Linux if you're on a

Windows these keyboard shortcuts might

be a little bit different we've got a

list of keyboard shortcuts in the git

repo associated with with this course

but if you just run that curl command

you'll see an output at the bottom down

here that says something like detected

your preferred shell is whatever your

shell is here and added Foundry up to

path run Source or simply start a new

terminal session to use Foundry up and

once you run that we can go ahead and

run Foundry up and this will actually

install an update Foundry to the latest

version now whenever we want to install

an update Foundry we can just run

Foundry up like this it'll automatically

install everything and Foundry comes

with four components Forge cast Anvil

and chisel we'll know we've installed

these right if we run Forge D- version

and we'll see an output that looks

something like this now something

important to note if you hit this trash

can in the top right this actually kills

the terminal it's different from the X

which is just close the panel we close

the panel and then we reopen our

terminal by hitting terminal new

terminal like this this actually creates

a new terminal which we can kill

like this but our old terminal is still

up in order to actually delete this

terminal we have to hit the trash can

now you want to try this out now delete

your terminal like we just did open up a

new terminal and run Foundry up if this

doesn't run we might have an issue with

your path and you might need to add

Foundry to your path if this is an issue

that you have please make a discussion

on the GitHub repo assed with this

course or check please first check this

lesson six of the GitHub repo associated

with this course and we'll add some

debugging tips to make sure that that

does indeed happen or if there is no

debugging tips here make a discussion on

the course but first be sure to check to

see if that discussion already exists

and you should be able to do Forge D-

version however what can happen is if

you trash can the terminal and open up a

new terminal if you run Forge D- version

now it might say Forge command not found

this means that you have to rerun this

command this Source command that Foundry

told us to do if you're working with

bash most of the time this bash RC file

automatically gets loaded but sometimes

it actually won't depending on what your

setup is if this happens for you another

thing that you can do is you can type CD

and go to your home directory and type

this line Echo source and then whatever

Foundry up told you to do double carrot.

Bash profile and hit enter for example

when we just ran Foundry up right here

it gave us this command here this Source

users patrick. bashrc that's what we

would want to Echo however this will

change depending on your terminal setup

so look to the GitHub repository for the

command that you should be using for

your setup please make a discussions

thread if one does not already exist

what this will do is it'll add this

command to the end of your bash profile

make sure you do double like this

otherwise you could override whatever is

currently in your bash profile now I'm

going to give you a command that if you

screw up you could accidentally override

some stuff if you've never used bash

profile before you kind of don't have to

worry about it though the other command

you can run is something like this if

you do get an issue we can just ask an

AI something like how do I get my do

bash RC to load by default and there's a

couple of different ways for this

depending on what system using and what

you're working with all I'm going to say

though is if this happens to you if you

run Forge D- version and instead of

getting an output you get something like

command not found ask an AI or come into

the discussions of the channel and as

people run into this we'll build and

start a discussion and if enough people

have issues we'll create a new file here

to help people debug that issue so what

it looks like chat gbt does give a

pretty good output of what we can do we

can edit our bash RC our bash profile

our profile Etc and work with it like

that so if you run into that issue

there's plenty of things we can do to

fix it don't worry but if you're a

little nervous feel free to use the

discussions channel of the course got it

okay great if you see an output like

this you've done it right if you see an

output like we don't know what you're

doing you've done it wrong all right

great and again installing these can be

some of the hardest parts of this course

so don't get discouraged if this doesn't

work right away if it worked right away

for you that's actually amazing

now also the control back tick shortcut

toggles the terminal visibility between

up and down I also have command J as a

toggle for panel visibility as well this

is a key binding that you'll see me use

pretty often because we often will flip

back and forth between the terminal and

our code which is going to be up here in

fact if we click this explore button on

the left we can select this area select

new file do something like

hello.txt or better yet hello. Soul

we're going to add some code in here

what's important to know is if you see

this white dot in the top section here

this means that this file isn't saved

command s or controls depending on if

you're on a Windows or Mac or Linux will

save it and make that white dot go away

unsaved saved unsaved saved it's

important to recognize if a file is

saved or not because if it's not saved

it might not do what you think it should

do so I kind of by default will always

automatically save by hitting command s

and it's a good practice to get into

just always autosave everything you do

we can also delete this file we just

created by right clicking it and

selecting delete move to trash final

thing that we want to install and we'll

install a lot of these as we go along is

actually an AI extension something in vs

code to help us actually have ai inside

of our Visual Studio code if you select

this little box looking thing that says

extensions you get a search box box

which allows you to search for

extensions the AI that I work with the

most is GitHub co-pilot but you can use

whatever AI you want or you could just

not even use an AI get a co-pilot does

cost money to use so feel free to also

not use it there's some other free vs

code extensions that use AI so feel free

to browse around and choose which one

you like for me I'm going to go ahead

and install GitHub co-pilot you'll get a

little guy in the bottom right for your

vs code that will let you know that

you've done it correctly you'll need to

sign into GitHub which is something that

we've recently made in order for it to

work now you'll see me using GitHub

co-pilot pretty often when I write my

code because I have this little doad on

down here I can start writing some code

and GI up co-pilot will start giving me

suggestions as to what I should write

for example if I were to add

spdx by since identifier get up copilot

actually automatically starts to gray

out and give me a suggestion if I tab I

can autocomplete my code with GitHub

copilot suggestion alternatively what I

could do then for example I could keep

coding and I can see it's already giving

me a suggestion here and if I hit upkey

enter I'll actually open up this bit on

the

side where get up co-pilot will give me

a ton of different solutions on what it

thinks I'm trying to write and I can

just pick one of these Solutions

obviously some of these aren't doing

anything we'll learn about about the

command pallet soon and we can also use

any of the GitHub co-pilot commands that

come with the command pallet an

alternate to vs code is a tool called

VSS codium so VSS code is a tool that's

owned by Microsoft and it sends up

Telemetry data up to Microsoft so

basically it can send data about ways to

make your experience better with vs code

for people who have a more security

mindset this is an open- sourced version

of vs code that I highly recommend you

check it out another extension that you

might want to add is GitHub co-pilot

Labs get up co-pilot Labs has AI

features that are experimental so it

might be worth installing as well all

right fantastic at this point you should

be 100% set up with Visual Studio code

and git if you're using git pod that's

great as well and if you're using

Windows you should be 100% using WSL

because the rest of the commands are

only going to work if you're using WSL

and we're only going to be working with

Linux bash or zsh commands moving

forward if you want to be a Hardo like I

was saying do everything in Powershell

that's great too moving forward what I

want you guys all to do is open up your

terminal the different ways I showed you

and create a folder by typing in mkd

foundary hyphen f23 and then you do CD

foundary f23 you'll notice something

else I do a lot is I'll type the first

couple letters of the folder I want to

go into and then I'll hit tab which will

autocomplete a lot of stuff for you in

the terminal sometimes it doesn't work

you'll get better at figuring out what

Auto completes and what doesn't I hit

enter this means I'm now inside of my

Foundry

f23 folder and I can run commands inside

of this folder moving forward I want you

to put all of your repositories inside

this folder this way moving forward in

the future when you start actually

working on projects in real life you can

refer back to this folder and refer back

to code that you wrote and refer back to

your notes to make sure that you

understand stuff moving forward we've

got git D- version Forge D- verion we

have cast d D version which cast came

with Forge and Foundry we have Anvil --

version and we also have chisle D-

version I'm going to type clear or hit

command K to clear everything in the

terminal and all right now that we have

everything set up let's go ahead and

start creating our simple storage

project in a professional environment

this is going to be the exact same

environment that the big protocols use

these are the environments that Unis

swap a curve Etc these billion dooll

groups use you are learning the exact

same tools as them additionally for

those of you who are interested in

security and auditing Foundry is the

most popular tool amongst Auditors so

for those of you who want to become

security researchers you're going to

learn the exact same tools that the best

of the best use you ready I sure am so

let's go ahead and create a new folder

inside of this folder here to do this

we're going to type

mkdir foundary simple storage f23 and

then we're going to CD into Foundry

simple storage f23 and you'll notice I

hit tab there to autocomplete again now

everyone's terminals are going to look a

little bit differently mine tells me the

exact path of the folder that I'm in but

I have a Alias called video shell which

just shows me the current folder that

I'm in and I'm going to use that for the

rest of the video so if you see my

terminal look like this it means I'm at

this location now if you're inside of

this folder you can actually type in

code and then hit a period and then you

should get a new Visual Studio code

which is now defaulted to that folder if

you don't you can also hit file open

folder and select the folder that you

want to open which will also open up a

new Visual Studio code inside of that

folder if you open up your terminal now

you'll see that we are indeed in in the

folder for this project and now on the

left hand side over here this Explorer

piece we create a file you'll see it pop

up in the left hand side of our Explorer

touch is a command to create or touch a

file and we go ahead and click it and

type stuff in this file now all these CD

and mkd and all these commands are known

as bash or zsh or like Linux terminal

commands and we're going to be using

them a lot throughout this course if you

want it's a great lesson on working with

bash and CCH and Linux commands on the

free Cod Camp YouTube but at the same

time most of the time chat gbt and most

AIS are actually very well-versed in

bash and Linux commands so anytime you

have a problem doing something you can

often just ask one of these AIS and it

can help you out as of recording this

one just came out a couple weeks ago so

it's incredibly up to date so if you

want to get the basics down it's only

about 45 minutes long I definitely

recommend watching this so you can at

least be familiar with some of the power

that Bash has you can absolutely

continue on with the course as is and

just use AI to augment you but for those

of you who want to get more knowledge

definitely check that out and again the

reason I have this- f23 is to let

everyone know that this is associated

with The Foundry

2023 course but awesome we can actually

begin getting set up with our own local

environments similar to that remix VM

that we saw when we were working with

remix we can work with our own local

blockchain and do a bunch of stuff

locally as you can tell by the name of

this project and from what I was saying

earlier this is going to be our simple

storage project but coded with Foundry

which again is a smart contract

development framework that's going to

make our deployments and interactions

with our code much more professional to

get started with Foundry what we can do

is we can open up our Explorer to see

what's in here let's go ahead and delete

high. txt move to trash I'm going to do

my video shell command here which won't

work for you but it works for me what

we're going to do is we're going to run

a command to create a new Foundry basic

project for for us and if you go through

The Foundry documentation this is going

to be basically this creating a new

project section of the documentation and

if you want to follow along with the

documentation you can do that as well

but to do this we're just going to run

Forge in knit like this and we'll see it

created a ton of folders over on the

left hand side for us and if you run

into an error because you accidentally

have some files in here for example if I

run Forge init right now it's going to

say oh it's not an empty directory what

we can do is type Forge init D- Force

period to say let's do it in this

directory hit enter and it's actually

going to give us an error because it's

going to go hey it already has

everything that I was going to do so it

just it's just not going to do anything

but if you have files in here already

you just add this-- Force piece now if

you get a different error about git

Basel is actually going to help us

triage that so take it away and we are

getting this error and this is pretty

common don't worry reason is because

even though git comes pre-install it on

our WSL install we still have to

configure our username and our email so

we can just use this commands change

this one my actual email and now let's

also configure the username after we

have these configurations we can run

that command again P init hello fundry

and if we check this out we have our

first fundry project ready to be used

with all the things we are going to need

and let's walk through what we have over

on the left hand side here so we have

this GitHub slork flows file which we're

going to ignore for now but we'll

explain this later we have lib which

we're also going to ignore for now but

we'll explain later we have script with

a file in here which for now we're going

to go ahead and

delete we have SRC which is where we're

going to put all of our smart contracts

that we want to deploy right now it

comes packed with this counter. Soul

which we're also going to delete move to

trash and then we also have test which

we haven't learned about yet but we will

and for now once again you guessed it

we're going to go ahead and right click

and delete source is going to be the

main section that we're going to be

working with SRC stands for source and

you'll see in a lot of projects this is

where they put all of their main

contracts test is where we're going to

put code to test what's in SRC and

script is where we're going to put code

to interact with our contracts that are

in SRC get ignore is going to be files

that we're not going to push up to

GitHub if we push our code to GitHub

which is going to be really important

get modules we get ignore for Now teach

about that later and founder. toml is a

file that is going to give us

configuration parameters about working

with Foundry and as we go along in this

course we're going to update this folder

because we're going to update how we're

going to work with Foundry now for us to

get started here we're going to add our

simple storage code into the SRC or

Source folder if you close your remix we

can just come on back to the repo

associated with this course we'll scroll

down to to the remix simple storage

select the code base and we'll go here

and just copy all the code in here come

back over to vs code in an SRC we'll

right click new folder simple

storage. paste it in here and hit

save now one of the first things that

you'll notice is this is formatted

horribly it's just all white text this

cute little eth logo comes up which is

really nice but we want to way to

actually format this code correctly so

there are a lot of different vs code

extensions that actually will format our

solidity code for us one of them is the

solidity if we if we simply type

solidity in the extensions bar we'll get

a whole bunch of options that we can use

I'm a big fan of the hard hat solidity

extension even though hard hat is

another framework it also can format our

code in Foundry another one that a lot

of people like is the solidity visual

developer so that's another option if

you want to use that one

and this one by Juan Blanco is probably

the most used on the planet but we're

going to go ahead and hit install to

install this nomic Foundation solidity

vs code extension and if we go back to

our simple storage. soou you'll see it

is now formatted with syntax

highlighting similar to what we saw in

remix if it doesn't automatically

highlight for you here what we can do is

hit command shift p or control shift p

which opens up our Command bar here and

we can type in settings and we want to

open our user settings in Json you can

also hit code and then settings as well

in here and a lot of you might have

nothing in here so what you can do is

you create these little brackets to say

hey whatever is in here is going to be

our new settings and we want to type

these little quotes little brackets and

say solidity like this little set little

colon here some more brackets and since

I'm using GI up co-pilot it's even

starting to give me suggestions which

I'll explain much later but we could do

editor dot but you could paste in this

editor. default formatter NCH

foundation. hardhead solidity I'll have

this code in the repo associated with

this course so you can just copy paste

this if you want to I've got a whole

bunch of other stuff in here so I'm

going to go ahead and delete this though

but that way your solidity code will

default format using that hardhead

extension that we just installed great

additionally this

also isn't formatted very well so we'll

go to extensions we'll type in toml and

we'll install this better toml here

close this now if we go to Foundry doomo

we'll see this is now highlighted very

nicely too great now just remember

whenever you see this little dot here

this means that it's not saved so hit

command s or file save and do that a lot

the other thing that's really good about

us adding that default formatter is in

our code here you know maybe this isn't

formatted very nicely right maybe we

we've got this over here and and this

over here and it's kind of not looking

very nice here if I go ahead and save

without formatting it'll save it here

but what we can do is if we add that

auto formatter now if we do command

shift p again that brings this up this

command pallet up you can also get it by

hitting view command pallet and we type

format document it'll format our code

automatically depending on what

formatter we're defaulting to since we

opened our Json and we defaulted to the

solidity hard hat it'll automatically

format with that if your code isn't

autof formatting that's okay don't worry

about this too much be sure to use AI a

web search and the forums to get your

formatting good the other thing that I

like to do is we'll go over to settings

again we're not going to go to the Json

we're going to open the user settings

and we're going to type in format on

Save and we'll check this box on this

way every time we save it'll

automatically format so if I have this

and I hit save it'll automatically

format my solidity code for me if I

don't want it to format again we open

the command pallet with command shift p

or view command pallet and we can say

save without formatting and it'll save

it see the white dot is gone and it will

not be formatted but I'm going to save

and reformat it because I like it

formatted and just to note we pretty

much never want to open these default

settings Jason so avoid that one

all right great and just with this

little pieces of code and Foundry

installed we can go ahead and compile

our simple storage. Soul right in our

terminal so what we can do is we pull up

our terminal and we can type in Forge

build or Forge compile and this will

compile our code like so once we compile

we see a couple new folders show up one

of them is out and this file in out has

all the different information that the

remix compiler would have for example it

has the ABI we go back to remix we go to

the compiler tab we go to one of our

contracts we scroll down we can see we

have the ABI section or it's also in the

compilation details in vs code we can

even click this little drop down thing

next to it and it'll minimize the ABI

and we can see the rest of this stuff

like B code method identifiers and all

this other stuff which we'll learn about

later we also get this cache folder this

is a folder that you could basically

ignore now anytime in our terminal we

hit up we can actually cycle through

commands that we've recently run so if I

run some crazy long command like this

Echo here which is a bash command don't

worry about it and I want to run it

again I can just hit

up all right great so one of the things

that we did in remix quite a lot was we

deployed our code to a remix VM or a

JavaScript virtual environment we want

to be able to do the exact same thing in

Foundry in order to test and interact

with our contracts Foundry actually

comes built in with a virtual

environment in the shell and if you run

Anvil you'll get an output that looks

and we pull this to the top you'll get

an output that looks something like this

Anvil and we get some fake available

accounts with some fake private Keys

you'll also get a wallet pneumonic the

derivation path which you can ignore

some details about the blockchain and

then this endpoint or RPC URL which

we're going to learn about soon for now

if you want to close this hit contrl C

or just delete your terminal to end

running the Anvil blockchain now moving

forward we're going to work with Anvil

but I do want to give you an

intermediary step that's going to be

with the ganach eth chain and we'll have

a link to this in the GitHub repo

associated with this lesson ginach is a

oneclick blockchain and gives us a user

interface or an app for us to look at

our transactions in an easier way so if

you go ahead and download it for your

system we can get started there now a

note for Windows users if you're using

WSL the setup here is a little funky we

ran into some issues with it in our

previous course and we'll have some

troubleshooting tips for those of you

who are using Windows and WSL if you

want to work with ganach everything that

we're going to be doing moving forward

though does work work with Anvil ganach

just allows us to see transactions a

little bit better than viewing all this

stuff in the terminal so if you're

having a hard time with ganache don't

worry we can do everything that we're

doing with Anvil which should work for

you no problem once you have ganach

installed when you open it up it'll look

something like this and if we hit quick

start for ethereum we'll actually create

a brand new locally running blockchain

with a nice little UI to view things

same as Anvil and same as REM we get

some addresses we get each of them has

balances they come with some dummy

private keys and dummy addresses and the

likes what's nice about this is that we

can see the blocks we can see different

transactions and if we're working with

truffle we can see contracts we're not

going to work with truffle though but

these are going to be very helpful for

us to view stuff additionally we're not

going to use ganache again in the future

so if you have trouble setting up with

it don't worry just use Anvil I'm going

to use it to show you what's going on

remember though

don't use these private keys on a public

blockchain it's for development purposes

only because everyone knows these

private Keys cuz they're dummy private

Keys now in order for us to learn how to

actually deploy to this blockchain or

how to deploy to Anvil if we're working

with Anvil we need to understand how

even remix was able to deploy to a

public blockchain when in remix when we

switch to injected provider of metamask

we know that metamask popped up it asked

us to add our password and we went ahead

and got connected and if we looked in

metamask we saw our account is indeed

connected to saoo when we hit deploy our

Rass popped up again and it was able to

deploy our contract to a real test

Network well how did it know where to

send our transaction how did it know

where to send our contract well let's go

ahead and open up our metamask here if

we click the three little dots and hit

expand view we hit the little button now

and we go to settings and we go to

networks you'll actually see in here

that each one of these Networks ethereum

mainnet Gil sapoia Linea or whatever you

have comes with a whole bunch of

information let's go to eth mainnet and

check that out for a second it has a

name an RPC URL a chain ID currency

symbol and block Explorer this RPC URL

is the actual https endpoint that we

actually send API calls to when we're

sending transactions so whenever you

interact with metamask and you send a

transaction or you deploy a contract

you're actually making an API call to

whatever is in here you'll see this is

an infura endpoint and infura is known

as a node as a service project that

allows you to send transactions to a

blockchain node without having to run

one yourself if you wanted to send

transactions to your own blockchain node

you would just Swap this out with your

own blockchain node address we can't

actually change the ones that come built

into mamass but we can add new networks

which is what we're going to do now in

here if we scroll to the bottom we can

hit add Network manually and we can add

information about our own custom Network

so for us we're going to make this new

network called local host or local chain

or whatever you want to call it for RPC

URL if you're working with ganach it's

going to be this RPC server right here

if you're working with Anvil at the

bottom we have this listening here so

what we would do is we would copy this

or we would copy this from ganache and

paste it in here just note that you

always need the HTTP or https col slash

most of our local applications aren't

going to be https they're just going to

be HTTP so if you're working with ganach

let's go ahead and copy the ganach

endpoint paste it in here like so every

single blockchain gets their own chain

ID it's an easy way for us to know which

blockchain that we're interacting with

gach has 1337 and Anvil doesn't say it

but it's 31 337 so Anvil is

31337 since I'm using the endpoint here

I'm going to typee in 1337 if you're

using Anvil it would be

31337 but what's kind of nice is

metamask can actually identify what

you're using and identify the chain ID

and basically tell you what chain ID to

use just a note it looks like the newer

versions of ganos are using a different

RPC server and a different network ID

and make sure you're on this hard for

the merge here as well although in

practice I've found that even when you

have

5777 it still is expecting 137 7 so be

sure to use the correct chain ID when

you're working with this currency symbol

we're going to do eth and since this is

a local blockchain we don't actually

have a block Explorer ether scan has no

way to connect to our own local

blockchain so we don't get a block

explore for this one but if I go ahead

and hit save now it says Network added

successfully and I can go ahead and

switch to my local host chain boom and

now we can see it in my list of networks

of Local Host I've got no asset no nfts

and no activity now if your local Anvil

or ganache chain isn't running after

you've put it in your metamask if you

actually try to swap to your Anvil or to

your local host or to your ganache

you'll just get this spinning wheel of

death here right and eventually you'll

get this little a that'll show up and

you'll have to switch to a different

network so if you ever want to switch to

one of these that isn't running it won't

work you'll have to either run it or you

can hit X here and then in your metamask

you could just delete one of these right

here while while we're not running our

ganache or our Anvil we're just not

going to have one of these selected

great and so this is where on both Anvil

and ganache they have these available

accounts in these private keys since I'm

using ganache what I can do is I can

select this show Keys copy this private

key and import it into my metamask so I

can go up hit this little button I can

hit import account paste my private key

in here and hit import now you'll see in

my menas I have a couple different

accounts account three the one I just

imported has 100 eth why does it have

100 eth well because I'm using one of

these dumm accounts from ganach and

again if you're using Anvil they have

they start with a th000

eth this process that we just did to add

our new ganache local chain is also how

we're going to add any evm compatible

chain on the planet we'll just hit add

Network and metamask actually comes

built in with a lot of these and for

example if we wanted to work with

arbitrum 1 we could just hit add and it

would add all this information in for us

approve Network added successfully but

if metamask doesn't have those built in

that's the process now if we go back to

settings network Local Host this

endpoint is the most important thing you

need to send a transaction to a

blockchain you need a connection to a

node in order to send transactions to if

you wanted to send transactions to your

own node you would run something like G

which is an execution client and then

something maybe like teu a prism which

is a consensus client and send

transactions there I'm not going to go

over this right now but I highly

recommend that those of you who are

curious maybe you take some time and you

try to run your own ethereum node I run

many ethereum nodes and it's a lot of

fun that's kind of a weird thing to say

it's fun to run nodes whatever it is fun

to run nodes each one of these

blockchains has different methods you

could send to them to do things if

you're familiar with apis and HTTP

endpoints and you go to this ether eum

jsonrpc

specification site you can actually see

all the different methods that ethereum

blockchain nodes can make and most evm

blockchain nodes can make and when we

actually sign and send transactions it's

these calls that we're actually making

like e sign sign transaction send

transaction send raw transaction Etc

we're actually not going to be going

over interacting with these because

Forge actually handles a lot of sending

these transactions itself if you want to

learn how to send a raw transaction

making raw API calls to your own

ethereum node or an ethereum node as a

service like infura or Alchemy you would

do that in a different programming

language like bash python or

JavaScript all right awesome now that we

have our endpoint and our private key we

pretty much have everything that we need

to deploy to our own local blockchain be

it ganach or Anvil same as working with

a real blockchain we need an actual

balance to spend gas to deploy our

contract now there's actually two ways

that we're going to learn to deploy

contracts and the first way is actually

with just working with the command line

if we're in our command line if we're in

our terminal here and we do Forge d-el

we can actually see all the different

commands that Forge comes built in with

the one we're going to be working with

right now is this create command and if

you read it it says it deploys a smart

contract which is perfect that's exactly

what we want to do and if we're in our

Command here let's hit clear and we do

Forge create d-el we can you see a ton

of different options for deploying our

contract click show Keys copy the

private key again if you're using Anvil

use the private keys there if we do

Forge create simple storage which is the

name of our contract it'll compile and

then it'll throw an error actually or it

might actually work but because I'm

working with this RPC server but this

RPC server is different from the one

that Forge actually defaults to so

instead what I can do is Forge create

simple

storage-- RPC URL copy this paste it in

here it might be upset with the

uppercase so let's just make that

lowercase and I'll hit enter and this

won't work either well of course we

forgot to add a private key so if I hit

up I can hit--

interactive as well and now it'll prompt

me for a private key now and a really

important note that I want to tell you

never use a real private key in your vs

code if you're using an application that

potentially will send your information a

much better option is to use your own

terminal as opposed to something like vs

code which might send data or get pod

since we are just developing and we're

just practicing it's fine to paste our

private Keys here because this is a

private key that's not going to have any

real money right it's a fake private key

so for now we can go ahead we can go

back to our ganache or back to our envil

hit show Keys copy this private key key

paste it in here it won't show up if you

hit paste but I'll hit enter and we'll

go ahead and see information about our

transaction now if you're working with

ganach we can now hit done here we go to

blocks we see we created a new block we

go to transactions we can see that we

sent a transaction and we created a

contract and then you can see logs about

working with this as well fantastic if

you're working with Anvil and you send a

transaction you're not going to see any

of those details for those of you who

want to continue to see these blocks and

these transactions and want to keep

working with ganach feel free to do so

moving forward we're going to work with

Anvil so I'm actually going to close

ganache now I'm going to hit clear in

the terminal and I'm going to run Anvil

here and what I'm going to do is I'm

going to create a new terminal by

hitting the plus button here and we're

going to run that command again but

we're going to run it with a private key

from Anvil so if we go to here we do

Forge create this time we don't have to

put an RPC because Forge defaults to the

Anvil one but I can say simple storage

inter active it'll do enter the private

key I will paste it and we'll go ahead

and deploy go to Anvil we don't get any

logs like this but we can see we went

ahead and actually deployed it to our

Anvil blockchain awesome work another

way we can do this Forge create is by

running Forge create simple storage if

we wanted to be incredibly explicit we

would do D- RPC C- URL copy this

HTTP col paste it in there-- private key

and back in Anvil copy the private key

paste it in like this and we will get

the same

thing now here's what I'm going to tell

you and this is incredibly important

pasting in your private key like this is

no bueno very bad we pretty much never

want to have our private key in plain

text

especially our production or our private

keys with actual money putting this

private key in PL Tex is not a big deal

because this is a fake dummy one it's

also bad to have our private keys in our

shell or bash history if I hit up once

on my terminal I can see the private key

in here which is why the interactive is

a little bit better because it at least

offis skates the private key to remove

your private key from your history in

bash you can do history- c now if I hit

up I can't see any commands and if I do

history I can see my entire history

which is just the history keyword now if

I type clear I'll do history now I see

history clear history great and we don't

have the private key in our Command

history anymore we will learn more about

proper private Key Safety in the future

but I want you to do something for me

right now in a new file I want you to

rightclick and I want you to write

promise. MD we're going to hide the

terminal and in here we're going to say

I promise to never use my private key

associated with real money in plain text

in fact take this and tweet this I

promise to never use my private key

associated with real money in plain text

and I can't spell and that's fine and

then if you want to add me or you want

to add cyron audits or whatever go ahead

and send that we are going to have more

of these promises that you're going to

do but this is the first one that I need

you to understand right now it's cool

because these are dummy keys but in the

future it will definitely not be cool

and I'm stressing this because I've seen

a lot of multi-million dollar companies

not follow this and get their private

Keys hacked great now of course though

the basic way to deploy to any

blockchain would be Forge create the

name of your contract add the RPC URL

and then add your private key we're

going to learn how to get RP crls for

free using Alchemy for any blockchain

that we want and like I said more safe

private key methodologies in the future

but now you've just learned how to

deploy your contracts to any chain from

the command line this is

great all right great so now we've

learned how to actually deploy a

contract to any blockchain that we want

using the command line now I'm going to

teach you the second way we're going to

deploy our contracts and and this is the

way we're actually going to do it for

the rest of the course when we're

deploying our code we want to make sure

we have a continuous reproducible way to

deploy our smart contracts and when we

test our code in the future we want the

tests to test the deployment processes

as well as the code so instead of just

doing the command line we're actually

going to write a script for us to deploy

our code and because Foundry has

everything written in solidity this

script that we're going to write to

deploy our code is also going to be

written in solidity and this is where

solidity as a contract language versus

solidity as a scripting language is a

little bit different Foundry has a whole

bunch of built-in stuff to give our

solidity even more functionality outside

of just smart contracts and you'll learn

about how later in the course but for

now we're going to learn how to create a

script to deploy our simple storage

contract and the way we create a script

to do it is first we come to our script

folder we'll rightclick new file we'll

create deploy simple storage.

s.o this S.L is just a Foundry

convention most of the time scripts have

a s doou instead of just being doou and

in here we're actually going to write a

contract in solidity to deploy our smart

contract which sounds a little bit weird

but don't worry too much about that this

deploy script is going to be written in

solidity but it it shouldn't be

considered a contract that we actually

ever want to deploy it's just for

deploying our code but it is written in

solidity so since it's written in

solidity we'll do the same thing as

usual spdx license identifier MIT and if

you're using GitHub co-pilot it might

even Auto suggest like this and I'm just

going to go ahead and hit tab I'll do

pragma solidity

0.818 and then I'll create contract

deploy simple storage like so and I'll

hit save if you go to The Foundry docs

we can actually scroll down to this

solidity scripting section in the

tutorials and you can learn how to

actually write scripts and work with

scripts the first thing that we need to

do in order to tell that Foundry that

this is a script is we need to actually

import some additional code now one of

the things that we saw in here was this

lib folder and this lib folder actually

starts with another folder called Forge

STD this Forge STD stands for Forge

standard library in here there's a ton

of helpful tools and Scripts for working

with Foundry and to tell Foundry that

this contract deploy simple storage is

actually a script we need to import from

Forge STD so we're going to do import

Forge

dstd script. soul and we'll have our

contract deploy simple storage inherit

all the functionality of this script by

saying is script and I know we learned

about inheritance before so you should

know what that means is script and then

additionally our deploy simple storage

is is going to need to know about our

simple storage contract so we'll go

ahead and import that import we'll go

down a directory since we're in the

script folder and we need to go to the

SRC folder these two dots is how you go

down a directory we'll do slash SRC vs

code even might help prompt you here

Dash and it again Auto prompted for me

and I hit Tab and now we've imported

simple storage now since we know that

this is the noob way to do Imports we're

going to do the cool way by using named

Imports instead of nameless Imports okay

great now inside every deploy or script

contract we need our main function which

is going to be called run and this is

going to be the command that gets called

when we go to deploy our contract so

we'll create a function called run we'll

make it external and we can have a

return a simple storage contract and in

here we're going to use a new keyword

that we haven't used before we're going

to say VM start broadcast VM is a

special keyword in the Forge standard

Library the VM keyword is a special

keyword that we can only use in Foundry

it's related to something called cheat

codes we're not going to go over that

too deep right now you can see a whole

list of Foundry cheat codes in the

documentation and Forge standard Library

references which have even more cheat

codes as well this VM stuff is only

going to work in Foundry if you actually

were to try to deploy this in remix or

some other framework it wouldn't work

these VM cheat codes only work in

Foundry it's not valid in regular

solidity but if we're inheriting Forge

STD code this VM keyword exists if

you're using the hard hat solidity

extension we can actually control or

command click into VM and we can

actually see where it's defined but if

that's confusing ignore that for now

this vm. start broadcast says hey

everything after after this line inside

of this function you should actually

send to the RPC and then when we're done

broadcasting we're going to do vm. stop

broadcast so everything inside of these

is what we actually want to send and

deploy the reason we have this is

because maybe we have some stuff like we

want to set some boilerplate code before

we actually send transactions and we

don't want to spend any gas to like set

starting value to one right so any

transaction that we want to actually

send we need to put in between these vm.

start broadcast and vm. stop broadcast

and for us to deploy our simple storage

contract we just do simple storage

lowercase simple storage right these are

different simple storage the variable

simple storage the contract equals new

simple storage like this and remember

what does this new keyword do well the

new keyword creates a new contract in

solidity it's also going to create a new

contract in between our VM dostar

broadcast this being in between these VM

dostar broadcast is going to send a

transaction to create a new simple

storage contract if this is a little bit

confusing for you right now that's okay

it's going to make more sense as we go

on later in the course but for now just

do this and follow along with me and

then of course we can say turn simple

storage okay great now if we pull our

terminal back up

we can see we have Anvil running right

now we can actually kill it with contrl

C we'll clear to the top and what we can

do now is run Forge script script deploy

simple storage. s.o hit enter and look

oops looks like I got some different

solidity versions let's change this to a

carrot in here let's change this to a

carrot in here this being an 18 so that

they're both on the same version let's

type clear close these or minimize these

out we'll hit up twice and we'll run

this again and now what you'll see is

it's compiling it compiles both the

script to deploy and our simple storage

contract using 0.8.9 because we did the

car compiler successful script

successful tells us the gas and then we

went ahead we returned our simple

storage contract which was deployed here

now you might be asking wait wait wait

wait Patrick we we don't have Anvil

running we don't have a local blockchain

running where did this deploy to well in

Foundry if you don't specify an RPC URL

it'll just automatically deploy your

contract or run your script on a

temporary Anvil chain so once I ran

Forge script it saw there was no RPC URL

so it spun up a temporary Anvil

blockchain deployed our simple storage

and then tore it back down at the end

you can see at the bottom if you wish to

simulate on Trin transaction pass an RPC

URL so if we do clear we run Anvil and

then create a new terminal we could run

Forge script script deploy simple

storage at s.o and I'm hitting tab to

autocomplete that-- RPC URL go back to

Anvil copy this go back to bash

HTTP slash we actually almost deployed

this to the blockchain we actually did a

simulation of deploying to our chain

here it gives us one more piece of

information to broadcast these

transactions add-- broadcast and wallet

configurations to the previous command

and now we get a new folder which gives

us information about our previous

deployments in case we forget for

example if we deploy a contract we can

flip back here and see where we actually

deployed code so let's pull up our

terminal once more and actually deploy

this to the blockchain so we'll hit

clear I'll hit up we have our RPC URL so

now let's do D- broadcast and we'll do

D- private key and we'll grab a private

key from Anvil and paste that in here

and hit enter boom and we see at the

bottom onchain execution complete and

successful we see we get some

transactions here we waited for receipts

Etc so fantastic so we learned how to

actually deploy our smart contracts

through these script in command now

awesome

job now let's learn a little bit more

about what actually just happened right

because right now sending transactions

is still kind of this magic thing right

so let's hide our terminal and let's go

up to our Explorer let's pull this out a

little bit and let's go into here now

what's important to note is that there's

actually a couple different folders in

here dry run is the folder whenever we

don't have a blockchain running

otherwise this gets separated by

chain ID and we'll talk about this a

little bit later but if we go into one

of these either dry run or or even just

run latest we'll see details about the

transaction we'll see a hash transaction

type contract name address blah blah

blah this right here this transaction

section is actually what is getting sent

on the Chain when we do Forge script or

Forge create this is the transaction

that we send to that RPC URL right this

is the API data if you're familiar with

https post this is the data that we

actually sent send we send the type

which for now just everything is type

two because we're in the merge don't

worry about type one for now we have a

from which is of course the from address

that we want to have we have a gas here

and this is the hex value of gas now if

we pull our terminal back up we'll clear

this out I'm about to show you an

amazing trick that's going to make your

life a lot easier Down the Line cast

actually can convert between hex and

numbers really easily and cast comes

built in with Foundry we do cast D- to

base paste our hex in here and write DEC

for decimal it'll convert this hex value

to its decimal value 0x 714 C2 whatever

is just this number and I use this cast

to base all the time you can put some

value in here and then what you want to

convert it to and it's a very easy way

to see what some value is there's some

other stuff in cast as well if you do

cast d-el there's some other ways to

convert different units to each other

like from way spites 32 and some other

stuff but two base is going to be one

that we're going to use a lot so we have

the gas we have the value with the

transaction yes since deploying a

contract is just a transaction we can

add a value to it if we want in our

deploy script right in here we would

just do some brackets we would say like

value and like one ether if we wanted to

deploy this with one ether we can't send

a value here because in solidity you

can't set the option value if the

Constructor is not payable we'd have to

make the Constructor payable but we

could send value just like any other

transaction there's this huge data piece

here this is actually the contract

deployment code and the contract code in

here we have the nuns which is going to

be that number that's only used once and

then don't worry about access list for

now but this is all the transaction

information and then of course we have

our RPC now what's not stored in here is

is a couple other pieces of the

transaction and additionally there are

these v r and s values that count for

the transaction signature it's not

getting saved here because it's

technically part of this from anyways

they're public values and these RS andv

allow our private key to sign the

transaction so what's really happening

when we send this the reason we need our

private key is we need the private key

to actually sign the transaction that we

built and that's happening a little bit

under the hood so whenever we send a

transaction there is a signature

happening we are signing a transaction

and then we are sending it and that's

important for later in the course they

don't save it here but signing the

transaction does happen when you sign a

transaction it's very similar to doing

that hex thing we showed you way way at

the beginning of the course with the

blockchain only the private key can sign

the transaction this is how when we send

our data to a node it knows that it's

able to execute it because it's signed

by our private key I'm not going to go

too deep into that right now this nuts

piece is a little bit important every

single wallet

has a counter of transactions which is

basically the nuns whenever you send a

transaction you give it a nuns or this

value this number only used once to

basically count your transactions this

is really good because if you want to

replay transactions you would just send

the same transaction data with the same

nuns for example if we have a

transaction that didn't go through

you'll see that this is in this run

latest with the dry if we run this again

if we hit up you'll see that if we run

our transaction again with our Anvil

deployed here we'll actually deploy

another transaction if we go back to our

broadcast folder we see there's actually

two runs and a new run latest if we go

to our run latest now you'll see that

the most the latest run now has 0x1 so

this increments every single time we

send a transaction your nuns increments

every time you send a transaction and

again contract deployments are

transactions now we went over a lot of

stuff in here but the most important

takeaway I want you to have from this is

anytime you change State on the

blockchain it does it in a transaction

and the differentiator is going to be

what's ever in this data field this data

field contains the op codes to tell the

blockchain hey I'd like to create a new

contract we're not really going to go

too deep into what these op codes are or

this evm bite code we'll briefly talk

about op codes later in this course but

if you want to really learn about op

codes and assembly we have another

course on security coming out that we'll

go over that but this is the most

important thing to take away when we're

in remix and we're sending transactions

with these buttons we're doing the exact

same thing we're populating the data

field of a transaction but instead of

the data being associated with creating

a contract the data is associated with

sending a

transaction right great now that we've

actually deployed our contracts though

we should learn how to interact with

them in the same way that remix allows

us to interact with them with our

buttons here now there's two ways to

actually interact with our contracts one

is going to be doing what we did before

with scripts but the other way is

actually going to be doing directly from

the command line so we're actually going

to learn the command line Parts in this

project and then we're going to learn

how to do scripts in a later project so

let's pull up our terminal here and just

to make sure that we have this deployed

let's hit up a couple times and we'll

rerun this deploy script now in just a

second we're going to learn how to

actually interact with our contracts

from the command line as well similar to

how remix has all these but buttons that

we can press however first we're going

to make this a little bit better and

we're going to take a couple of

different approaches to not having this

in the command line as you saw before we

could use Forge create interactive paste

our private key in and it wouldn't be in

our command line we actually can't use

interactive for when we're sending

scripts at the moment I'm sure in the

future they'll make it a little bit

easier for us to do this but right now

we really don't want to have to do--

private key and paste our private key in

PL Tex so what else can we do what

alternatives can do we have now what I'm

about to show you once again only do

this for your development environments

do not put a real private key in here

the reason I'm showing you this is

because it is much quicker to test

however it's terrible to use in

production so this is cool for

development purposes this is not cool

for actual production purposes what

we're going to do is we're going to

create a new file called EnV and

whenever you create a EnV the first

thing you should do is go to a g ignore

file make sure that a EnV is in this G

ignore I'll explain what the dog ignore

does in the future but for now just have

that be the first thing you do in our DV

file we can put in what's called

environment variables these are

variables that might be a little bit

sensitive that we don't want to actually

write in the command line or

accidentally expose to the public one of

those of course is going to be our

private key so let's go to Anvil scroll

up grab that private key copy and paste

it in here and we have this private key

equals this typically you'll also see

RPC URL equals what's our Anvil RPC Rel

let this right here so we'll do

HTTP SL slash paste that in there and

great now that we have those in there

what we can do is now run source. EMV

which will add these environment

variables into our shell here and we can

do Echo private key like that and we'll

see our private the key actually show up

like so we can also do Echo dollar sign

RPC URL and we'll see our RPC URL

actually show up like this and then what

we could do is we could go back to our

Forge script and instead of typing in

our private key we would just do dollar

sign private key and dollar sign RPC URL

so now our RPC URL and our private key

at least aren't being run in our command

line so that it's not stored in our

Shell's history the issue of course is

that okay well now we have it stored in

this EnV anytime you have your key

stored in plain text you should be

afraid you should be a little bit

nervous so we can actually take one more

step to make this even more secure and

this is going to be one of the steps

that I recommend that you take when

you're actually working with production

code you definitely do not want to

launch production code with aemv file

and I'm going to summarize all this very

soon just stick with me I promise this

is a little bit boring but it's

incredibly incredibly important that you

get this right and I'm going to try to

prevent you from getting wrecked now

Foundry is a tool that is constantly

being improved and updated and there's

an issue in The Foundry repo right now

called improve wallet management us

using key store I would love a way for

you to actually encrypt your private

keys so that none of you accidentally

push a private key up to GitHub or

expose a private key that it's in PL

text if you run Forge script d-el and

you scroll up you get this wallet

options section where you can actually

pass the path to an encrypted key store

file and a password a key store is a

file that has your private key but

encrypted by a password instead of

having your private key in PL text you

would have it encrypted and you would

just need the password to decrypt it

that is a much safer way to deploy your

contracts I've added some context in

another issue on Foundry as well and if

you all could come in here and give this

a thumbs up that would be fantastic a

way to encrypt your private key into a

key store file natively doesn't exist in

Foundry yet but I've put out a bounty

for someone to actually implement this

so be sure to just check the G up repo

associated with this course to check to

see whether this feature is implemented

so what I'm really trying to get at is

for the moment a private key in ourv

file is cool so long as we don't expose

the EMV file but for real money you're

not going to do that we're not going to

do that okay for real money we're going

to use the dashes interactive to paste

our private key or we're going to use a

keystore file with a password once

Foundry adds that there are some tools

like dap tools e sign that you could

optionally download if you want to

deploy and interact with wallets that

have real money in them and it does have

this import keyword where you can import

your private key into a key store file

and then you would just obviously

encrypt that with a password so for the

moment this is your setup but in the

future this is going to be your setup

okay this is cool now but not in the

future and additionally if you go to The

Foundry full course f23 you go to

discussions and this will also be in and

this will also be somewhere on this side

at some point you'll see this the EMV

pledge which has a whole bunch of

information about working withv files

and keeping your private key safer for

the rest of this course we are going to

be working with this syntax because it

is easier however I'm really hoping that

Foundry in the future adds this key

store encryption by default so that we

don't accidentally expose our private

keys and I'm not doing this to scare you

but I'm doing this to impress upon you

the importance of making sure you keep

that private key and that pneumonic safe

the other reason that we're okay to put

our private key in ourv file is that

you have already promised me that you're

only going to work with a development

private key or a private key that you're

not going to add any real money into so

if you expose it it'll be fine but you

still want to practice not exposing it

so please take some time to read this

and then if you do agree to everything

just say I will be safe as a comment on

this DV pledge so I'm going to read it

out and it's important for you to

understand this moving forward so it's

going to be a little dry here but I am

just going to read it I solemnly swear

that I will never place a private key or

secret phrase or pneumonic in ainv file

that is associated with real funds I

will only place private keys in ainv

file that have only test at eth link or

other cryptocurrencies when I'm testing

and developing I will use a different

wallet than the one associated with my

real funds I am aware that if I forget a

DOT get ignore and push my keyphrase to

GitHub even for a split second or show

my keyphrase to the internet for a split

second it should be considered

compromised and I should move all my

funds immediately this is a really

important line even if you show your

private key to anywhere on the internet

for even a split second it is considered

compromised and you should move all your

funds immediately if I unsure if my

account has real funds in it I will

assume it has real funds in it if I

assume it has real funds in it I will

not use it for developing purposes I

aware that even in my metamask if I hit

create account or add account on my

metamask or other eth wallet I will get

a new private key but it will share the

same secret phrase slne monic of the

other accounts generated in that

metamask these are some additions that I

made from the last course for this

course I will only use funds associated

with my brand new neverbe used metamask

or other wallet and again most browsers

you can choose a different profile and

install a metamask on a different

profile and use that metamask for this

development purpose if I must use a

private key associated with real funds

in the future until I'm 100% sure what I

am doing I will always either use

encryption methods like the DAP tools

keystore file I'm not going to show you

how to work with this because some of

the installs might be a little bit

tricky but they have a way to actually

import and encrypt private keys to a key

store file use the foundaries built in

key store Creator which is an

implemented yet anybody here who is a

rust developer or knows some rust or

wants to participate definitely be sure

to check out this issue which is on

Foundry and I would love somebody to

take a crack at this or if you must use

the command line as a way to pass your

private keys and then delete the command

line history immediately afterwards if I

never actually deploy anything to main

out myself or work with the private key

with real funds I do not need to be

concerned for any of you who are getting

a little bit nervous about this just

remember if you don't work with any real

money you don't have to worry about this

okay so a lot of you people who are who

are newer here who are going to be going

through this course we're not going to

use any real funds so you won't have to

be worried about this for those of you

who are doing the extra credit which is

with real funds you will need to keep

this some mind moving forward and I

would try to load your real metamask

with real money with small amounts so

that if it all gets stolen you won't

lose sleep at night okay great and I'm

telling you all this to arm you with

this knowledge that you can be more

secure moving forward take a look at

this read this internalize it and if you

want to copy paste this on Twitter in a

huge tweet thread shout this from the

rooftops put this in an article make a

tick tock with this Dov pledge have an

absolute blast the more people who know

about this and the more people who

understand this the better thank you for

coming to my TED Talk all right so I

know that was a lot of private key

information and there's going to be more

soon too so but the reason I'm harping

on this is because I really really

really really really want to make sure

that all of you don't actually mess this

up since you are the developers you are

going to be the ones responsible for

dealing with all this and I want to make

sure that you get it

right one final option that we can do as

well which again saves us from having to

have our private key and plain text is

going to be using something like third

web deploy so we actually have Kira from

the third web team team to explain third

web deploy now she is going to use the

MPX command which comes with nodejs and

mpm installation which we haven't gone

over in this course but we will leave

some links in the GitHub repo associated

with this course to download that if

you're interested so take it away Kira

in this video we're going to learn how

to easily deploy any contract to any evm

chain using one simple command this

command requires no setup hardcoded

private keys RPC URLs or scripting

required third web handles all of the

complexities for you because there's no

need to export your private key this is

much more secure the deployment is done

through the dashboard UI using your own

wallet so with that said let's jump into

deploying our contracts so let's say we

have cloned this repo or written our own

contract this can obviously be any

contract at all but I have gone ahead

and cloned this simple storage contracts

just to demonstrate how we can deploy

our contract as you can see in the

sidebar um so yes I've opened this up in

my code editor in the sidebar there is

nov file I haven't set up an RPC URL I

haven't exported my private key there is

no setup needed here I want to reiterate

this you do not need to pre-install

anything there are no dependencies so to

deploy our contract we are going to run

the simple command npx third web deploy

so what this done is detected our

project type which is Foundry and also

could be hard hat or Brownie and then it

has compiled our contract and then it's

allowing me to select which contractor

deploy so I'm going to select the simple

storage contract so this is now

uploading the contract metadata to ipfs

and it means that our contract is going

to be automatically verified if you

would like more details on how this

actually works then please go ahead and

visit the third web developer docs which

you can see here which is at portal.

third web.com SL deploy and you can read

all about how this works so what's

happened now is that a browser tab has

popped up in my browser um and this

allows me to deploy my contract from a

front end so if I had construct prams

which I do not in this case there are no

construct parameters um then I would be

able to fill these out from the front

end right here next what we need to do

is select the chain that we want to

deploy to as I said this can be any evm

network so we can select ones that are

pop such as bass or we could add a

custom network if this is not already in

the list but I'm going to select Mumbai

when I click deploy now this is going to

trigger two transactions the first one

is going to be the transaction to deploy

my contract the second one is going to

be a message which I will sign and this

is a gasless step and this just adds

your contract to your dashboard so that

you have a user interface in which to

interact with this contract a little bit

like

remix so I'm going to click this button

I'm just going to sign these two

transaction Cs and then I will be right

back as you can see our contract has now

been successfully deployed how easy was

that awesome so you can see the contract

address here which we can copy if we

needed to use that later I'm just going

to give you a very quick overview of the

dashboard so there's this build tab here

which just enables you to build your

contract into a front end with easy to

use hooks for different languages uh

Hooks and functions for different

languages uh the Explorer tab allows you

to see all the read and write functions

on your contract so you could add a

person and then input the parameters

here you can store list the people name

to favorite number and retrieve all of

the functions that we wrote in the

contract you can see and interact with

here you can see the events on the

contract and the source code as you can

see this was a super simple easy and

safe way to deploy your contracts using

third web third web is the fastest way

to build web 3 apps we can have sdks in

multiple languages we have pre-built

contracts we have a solidity SDK and

infrastructure for your web3 development

needs for more information please head

to third web.com or visit our

documentation and if you have any

questions please head to our Discord

in any case let's go ahead and let's

learn how to interact with these

contracts from the command line first

and in later courses we'll learn how to

do it from scripts so we have our Anvil

running and we've deployed our contract

using our deploy using at least

something marginally better using

private key as an environment variable

as opposed to just pasting it right in

here so what we can do now is we can

take this contract address and we can

actually start to interact with it

Foundry has another tool built in called

cast and if you type cast d-el you'll

see we get a whole bunch of commands to

work with cast one of the commands that

we can work with is going to be send

which is to sign and publish a

transaction so what we can do is we can

do cast send d-el we can see the help of

send and we can see the arguments it

takes is going to be two the signature

and the arguments so on remix for

example we have our simple storage

contract and we deployed it if we wanted

to call our store function in send the

transaction we would just add some

numbers in here and then click store

like this right if we want to call store

from the command line we can do cast

send the address we want to do the

signature which which for now just know

is the is the function and the input

types it needs so we could call store

with a parthy u 256 because we're

calling the function store which takes a

un 256 as input parameter and then the

arguments or the values we want to pass

to our store function and we'll go ahead

and hit enter of course this fails

because we need to add our private key

and RPC URL so we'll hit up we'll do RPC

URL we'll do dollar sign RPC URL and

then we'll do-- private key and then

private key like that and now you'll see

we'll get all of this data about our

transaction back we get the block hash

block number contract address is blank

probably because it's a local chain logs

we can learn we'll learn about logs

later the transaction hash Etc now in

order to read this we're going to use

cast call which is going to read off the

blockchain and if we do cast call d-el

and we scroll up a little bit we'll see

call takes two signature and arguments

exact same as send but the difference is

it's like call is like doing one of

these blue buttons it's calling as

opposed to sending a transaction it's

just doing a view function not actually

sending a transaction so we'll do cast

call we'll paste the contract address

we'll call retrieve r t r i v r e t r IE

V did I spell retrieve wrong I don't

know I guess we'll find out no input

parameters here and no arguments so we

can just hit enter and we'll see we get

the hex value back this is where I said

you're going to be converting stuff from

hex back and forth a lot then we do cast

d-2 base paste the hex and say decimal

and we can see we get back 1 2 three

which is exactly what we've stored on

chain so if we hit up a couple times

back to our cast send transaction our

cast send command and we change 1 2 3 to

777 we hit enter we'll send that

transaction now if we hit up three time

two or three times we'll call cast call

retrieve now and we should see the new

number which we get back as a hex and

then we'll do cast d-2 base paste it in

deck and we do indeed see 777 returned

to us awesome so now we know how to

actually interact with our contracts

from the command line and this is going

to be the same way we can actually

interact with our contracts on an actual

test net or on an actual main net

all right so now you might be asking

okay Patrick what does this look like on

a test net or a live Network so let's go

ahead let's go to ourv file and let's

update this so that it's aemv file for

an actual test net so the first thing is

we're going to need an RPC URL for an

actual test net for an actual Network

and this is where in our metamasks

actually have inferior connections built

in remember before we went to our

settings networks eum main net we saw oh

we saw we have this inferior connection

we can't use this one because this one's

designed specifically for our metamask

so we're going to have to get our own

RPC URL for an actual test net well one

of the things we could do is we could

run our own blockchain node but a lot of

people don't want to do that so what a

lot of people do is use something called

a node as a service to do this what I'm

going to recommend you do is actually

come over to The Foundry full course

repo scroll down down and there's going

to be a section called deploying to a

test net or a main net if we click this

link we'll actually go ahead and we'll

get sent to the Alchemy platform where

we're going to sign up for a free notice

of service that we can actually send

transactions to and we're going to go

ahead and sign up for their platform you

can sign up with Google sign up with SSO

whatever you want to do I'm going to go

ahead sign in with Google I'm indeed

human we're going to come to their user

interface that looks something like this

we're going to deploy this to sepolia

but remember go to the recommended test

n section of this course so what we're

going to do now that we're in here is

we're going to go ahead and create a new

app and you can name it whatever you

want I'm going to call it tooa testing

I'm just going to copy this for a

description this is on the ethereum

Chain but on ethereum spolia we're not

going to do any advanced features we'll

go ahead to create app and now we have

this ethereum seoa app where we can view

details we can see how often we're

calling this and we can see different

details about our notes Noe and if we

hit view key we see we have this https

endpoint and this is going to be the

exact same thing as that Anvil or ganach

or metamask endpoint that we saw and

we're going to go ahead and copy this

and back in our b v what we could do is

we we can create a new RPC URL called

sepolia RPC URL equals and we'll paste

that in here now we have an RPC that

points to an actual test St with our

private key we can't use this as our

private key because this is in Anvil

private key and it doesn't have any real

money in it and it doesn't have any

testet eth in it but what we can do is

instead we can use our one of our

private keys in our metamask so if we

switch back to sapoia in our metamask we

can pick one of our accounts that

actually has some money in it I'm going

to pick account number one we'll hit the

three little dots Account Details export

private key and remember it's okay for

me to show the private key here because

this is just a dummy private key but

I'll add my password in and remember I'm

never going to actually do any real

money with this and I'll copy this done

and paste this in here and maybe I'll

maybe I'll comment this line out inmv

file this hashtag or this pound sign is

what the comment is but maybe we'll do a

new private key equals and I'll paste

this in here and now I have the private

key for metamask I have the RPC RL and

those are all I need to actually deploy

a transaction so what I can do now pull

my terminal back up so we're going to

run this command to actually deploy this

to a real test net from our Foundry

using Alchemy as our node as a service

and you'll see in the user interface of

alchemy you'll see a transaction

actually come through our node This Is

Us sending a transaction to a real node

and we'll be able to see the stats here

on our Alchemy dashboard so let's go

ahead let's do this again so first we're

going to need to run source. AMV to make

sure all of our AMV stuff is loaded then

we're going to run Forge script script

deploy simple storage. s.o and I'm

hitting tab to autocomplete

here-- RPC URL sepolia RPC URL with the

little dollar sign D- private key dollar

sign private

key-- broadcast if you don't add the D-

bradc it won't actually send it it'll

simulate sending it now if I hit enter

we'll see a compile and now we're

running this script deploy simple

storage. s.o which actually deploys it

and we'll see we went ahead and deployed

our contract simple storage on the

sepolia Chain we see all these details

about it it's sending the transaction

right now it's storing the latest run

under the broadcast folder under its

chain ID in here in this run latest.

Json and after a brief delay we'll see

it went through and what we can do is we

can grab this hash go over to sea.

etherscan.io paste that hash in here and

we'll see we actually successfully sent

a transaction and if we click on our

contract address we just created we'll

see we actually just created this

contract on a real test name we go back

to our Alchemy dashboard and we hit

refresh we'll see we actually sent we

sent some requests we scroll down we can

see some of the different requests we

sent eth send raw transaction was the

request that we sent to actually send

our transaction to the blockchain but we

also got some stuff about the chain ID

fee history

Etc one thing that you'll notice though

when looking at this on ether scan is

that the contract o it's just a whole

bunch of bite code here right this isn't

very readable what we can do is we can

actually verify this contract and now

I'm going to show you the hard way first

and I'm going to teach you the easier

way later but you can manually verify a

contract

on ether scan or other block explorers

by selecting verify going to solidity

this is a single file contract so we're

going to do single file I know that we

were on

0.8.9 and our open source license is MIT

we'll hit continue we'll go back to our

simple storage. soul and we'll copy the

whole contract scroll down we'll hit

paste optimization is going to be yes

there's no Constructor args no contract

Library addresses no Miss settings I'm

not a robot and we hit verify and public

sometimes this can be a little bit

tricky to get right and we're going to

work with programmatic verification

pretty soon that makes it a lot easier

but if we did it correctly what'll

happen then is if we click on our

contract address here and we go to

contract and we scroll down we can

actually see our contract right in ether

scan this will also give access to these

read and right contract buttons which we

can see it now looks really similar to

what's on remix and we can actually

interact with our contract right from

etherscan or another block Explorer like

I said that's the manual way to verify

your contracts and you can run into a

lot of issues doing that so I don't

recommend doing it I recommend doing the

programmatic way which I'm going to

teach you very

soon all right so now we're just about

done with our very basic project here

which is fantastic we've learned a ton

already but there's a couple things we

want to keep in mind here moving forward

and one of those things is when it comes

to formatting so we are using the vs

code autof formatter to Auto forat our

code but if somebody else comes and I'm

going to actually save with without

formatting if somebody else comes to our

code base we're going to want to have

them format it the exact same way that

we format it so what we can do is we can

use the forge format command which if we

run it you see favorite number actually

went ahead and formatt it so I'm going

to save without formatting again run

Forge format and it's going to Auto

format our code here so this is a

command that will automatic format all

of our solidity code awesome and

additionally for every single repo you

ever work with you always want to make a

readme.md file so right click new file

readme.md I actually already made one

over here and this is where you're going

to put information about your project

here I put some notes about the private

key usage which I'm just going to delete

for now readme files are generally where

you put information about your project

instructions to work with it places to

contact you really any information that

another open ource developer should know

when they want to interact with your

project because we are going to push

this up to GitHub as well we're not

going to push this up to our GitHub

because it's kind of easy but in the

next project we're actually going to

push the code up to GitHub and I'm going

to teach you how to do that readme.md

are this markdown syntax remember how we

were talking about answering questions

or asking questions using markdown

syntax well this is going to be the

exact same if I do a hashtag or pound

sign like this and I say hello and then

some text down here and if I hit save

what I can do is I can actually preview

this markdown so in my extensions over

here we're going to look for a markdown

extension actually already have one

markdown allinone or markdown preview or

whatever you want to install and we can

do open up our Command pet with command

shift p or view command pallet we can do

markdown preview open preview like this

and we can see what this looks like as

if it was on a GitHub repo we can see

Hello is Big we can see our text down

here is small and if I were to do like

some back Texs like this I can say like

code here save that look at our preview

again we can see this is formatted now

as code you can also do command shift V

to automatically go to preview mode or

it might be control shift V for Windows

and Linux users there's a lot of

different ways to go preview your

markdown and remember if formatting your

your readme is difficult usually AIS do

a pretty good job at formatting your

markdown for you if you just ask them

politely

now Alchemy has a couple of other really

cool features about it especially when

it comes to learning more about what's

actually happening with our transactions

whenever we send a transaction to a

blockchain node it actually enters

something called the M Pool it's

basically the place where transactions

go before they get actually sent and the

Alchemy dashboard is a great place to

actually view those transactions and see

their status so I'm going to go ahead

and turn it over to veto from the

Alchemy team who's going to expl explain

more about what Alchemy has to offer

some of the other cool parts of alchemy

and more ZK Stark ZK Nar Z proof z Oh W

oh I'm I'm sorry I'm Jam Jam everyone

and welcome this brand new video I'm V

and today I'm going to walk

to this is not my

channel this is not even AR's Channel

what oh my God this is the latest

Patrick Collins video about Foundry that

everyone must watch oh well well welcome

everyone I am VTO and thank you Patrick

for hosting this comeu I guess my job

today is to tell you a bit more about

what Alchemy is what we do how we do it

and how you can get the most out of it

well before getting started let me

quickly quickly introduce myself I am

BTO lead developer experience at Alchemy

blog hand developer and web free content

creator on a mission to aboard 1 million

developers onto web free of course today

we're not here to talk about me but we

here to talk about how Alchemy can app

your decentralized applications scale to

billions of users so to get started what

is alchemy well Alchemy is a node

provider and web free developer tooling

platform powering hundreds of thousands

of web three and web to Applications out

there things like openc Nifty Gateway

but also zerox Argent Dapper but as well

as big massive web to companies such as

Adobe Shopify and stripe the question

here probably is why do these companies

use us why Alchemy well that's the

question we try to answer here briefly

the thing is when you need to develop an

application chances are you won't run

the servers you'll code your code will

run on and most likely you won't even

develop the deployment and integration

pipelines for it to do this you will use

services such as AWS Azure Google Cloud

well Alchemy does exactly this but for

web free you can see it as the AWS of

web free with apis sdks libraries that

will simply make your developer

experience better but how do we do that

well we do it in mainly three ways the

first one is the super node a blockchain

propriatary engene that acts as a load

balancer on top of your node and make

sure you always got the latest available

data from the blockchain on top of the

super node we built the announced apis

the announced apis are set of apis that

will allow you to pull data from the

blockchain with ease here you can see

how we envision this with the Alchemy

supernode at the center as the core

infrastructure powering its ecosystem

all around such as our announced apis

but also our monitoring tools and of

course supporting all the chains that we

support to date and we'll get back to it

in a few seconds but the question is of

course how do you get started well the

first thing that we're going to do is

navigate in on alchemy.com and we're

going to create a new account creating

an account on alchemy.com is completely

free and actually cool thing is that

you'll be able to scale your application

using our Premium plan because it's

quite generous so don't be concerned

about paying anything everything you'll

see today and probably in Patrick's

course is completely free to use let's

go back creating a new account in this

case I would just sign in of course I

already have an account so I click on

sign in and as soon as we'll open this

window you will see all of your

applications of course if this is the

first time you loging in on Alchemy you

will only see the demo application but

no worries we're going to learn how to

create a new application right now super

important click on create app and let's

give it a name so we're going to call it

Patrick is cool and I'm going to use

underscores just because of personal

preference feel free to use spaces or

name your application the way you want

we're going to also give a description

this is optional you don't have to but I

really think that Patrick is cool and

then we're going to select a chain as we

said before we support the majority of

evm compatible chains as you can see

here we support ethereum polygon P also

ZK evm as well as optimism and AAR and

on top of that we support Solana and non

evm chain here you can select your chain

and here you can select your network in

this case we will go for eum mayet but

feel free to try out all the other

networks and test Nets of course we have

one for all of these um main net that we

support so I will create the new app and

once the app has been created I can just

go and search for my name so Patrick is

cool and click on my application here we

go once the application has open you

will be able to see the application

specific dashboard and this is a big

change big game Cher for all de

centralized application developers

because this gives you full visibility

over your application and infrastructure

health you'll be able to see things such

as latency compute units that that is

how many RPC calls are eating your notes

as well as the success rate of your

calls the throughput and so on and so

forth super useful when you need to

debug so let's say that here you see 98%

of success rate you'll be able to

understand why your transactions are not

going through well let's actually do an

example let me go back and find an

application that has actual codes so

here we go I just navigated to this demo

key application that as you can see has

a ton of calls but also as you can see

it has a success rate of

98.5% that means that 1.5% of our calls

are failing to go through but how do you

understand that how do you debug this

well if you not using Alchemy chances

are that to debug your RPC calls you

will have to spin up your own nodes or

be run a local node and in that case

you'll be able to see the logs coming

from the node otherwise there is no

possibility to see the logs coming from

the node this is not something you will

see on E scan using Alchemy you'll be

able to see all the issues related to

your calls as well as the known issues

related to your calls in this dashboard

so let's say that we have 1.5% of call

not going through what we can do is go

on the recent invalid request dub and

here all the requests that didn't go

through will be listed as well as the

reason why they didn't go through for

example here we have an e Sand Road

transaction that didn't go through

because there weren't sufficient gas

funds but let's take another one here

execution reverted for example means

that probably there is a problem with

the smart contract so as you can see the

bugging as well as you can see other

information on the left hand side but I

will go back at this in a few seconds

because I want to show you another tool

that is even more precise to see the

information about the acttion request

here you'll be able to debug your RPC

calls with super Ease on top of that as

I was saying we have other tools to help

you debug and get more visibility on

your application so if you click on the

menu and here what we can do is navigate

on the M Pool and the manool is actually

just like the manool that you might

think about when you're thinking about

ethereum so it's a place where all of

your transactions are and you can see

the status of the transaction the

information about the transaction what

if the transaction is going through if

didn't go through if it's spending for

hours if you got mind how much it cost

and so on and so forth so let's say we

we just navigated on our mempo Watcher

and here we have all the transactions

going through on our applications here I

have a bunch of applications so that's

why I'm seeing a lot of transactions

here on the top you can see all the Mind

transactions so the transactions that

already went through like can me mind or

validated the pending transactions um

let me just select one application

because of course otherwise it's going

to take a long time here you have all

dep pending transactions that mean all

the transactions that are waiting to be

mined or validated and here you you have

dropped and dropped and replaced so

transactions that have been dropped

cancelled or replaced by other

transactions with the same non same call

data and the same gas fees or dropped

means there are transactions that have

been cancelled and won't be validated or

mind but on top of that you can get even

more information on these calls on these

transactions if I click here on the ash

this won't bring me on ether Canal will

bring me on the M poool transaction

summary page and here I can see all the

information about the transaction I can

see how much gas it costed uh which

network it was on of course uh the

transaction hash as well as the from

address so who send the transaction and

who's sending the transaction to as well

as the value inside transaction the time

it took to get sent and the time it took

to get um validated this is more clear

on validated transactions where

everything has already be filled out so

I can go back in my mind

page so here we go I can select one and

as you can see here I have all the

information so I have Max veper gas I

have the transaction type so this was

using the EAP 1559 and a bunch of other

information about the transaction itself

super helpful to debug and get full

visibility over it all right now that we

have quickly gone through how Alchemy

Works what it is and how it's features

can help your developer experience

become way better and develop faster I

don't want to steal much much more of

your time while learning during this

amazing course so what I'm going to do

is leave you with a couple of resources

that will make your developer experience

with Alchemy even better the first one

is our documentation so our

documentation has everything you need to

get started using our apis SDK libraries

and also tools that we didn't have the

time to go through today such as our

generalized custom graphql web books

that allow you to pull data real time

from the blockchain through graft

queries on top of that you will also

have tutorial and guides to build your

applications and complement the

knowledge you're creating during this

course of course follow us on Twitter at

Alchemy platform or Alchemy learn and if

you want to shoot me a message telling

me the amazing things that you're

building while learning from the

Patrick's course please shoot it at

vostock on Twitter thank you so much

Patrick once again for hosting us and

thank everyone for sticking with us for

12 minutes it's been a pleasure see you

around and happy building

but for this one you should be

incredibly proud of yourself you just

did an entire project in Foundry huge

congratulations so let's do a quick

recap of everything we learned and then

we'll move to the next project and yes

we are going to push our next project up

to GitHub and a lot more advanced

Foundry and a lot more advanced tooling

here so let's do a quick recap of what

we learned so far well first we learned

how to create new Foundry projects with

Forge Das Das and knit which will give

us all of these folders on the left hand

side here to actually start working with

our projects in a more professional

environment we learned about some of the

basic Foundry commands such as cast

Anvil and Forge Forge is used for

compiling and interacting with our

contracts cast is used for interacting

with contracts that have already been

deployed and Anvil is used to deploy a

local blockchain similar to ganach which

is another local blockchain that we

worked with we learned that whenever we

send a transaction on our metamask we're

actually making an HTTP post request to

this RPC URL

and we can also take an RPC URL from a

node as a service like Alchemy and use

it to actually send transactions from

our Foundry projects we learned both how

to actually compile our code in Foundry

and then also write a script to deploy

it directly in solidity we've learned

some very basic information about

keeping our private Keys safe for the

rest of the course we're going to be

working with aemv file but when we work

with real money we might not want to

actually have our private key in plain

text ever so we learned how to deploy

our contracts to a blockchain

programmatically and then we learned how

to interact with them using the cast

keyword and send to send transactions

and then cast call to read from those

contracts we've learned how to autof

format our contracts with Forge format

and we learned the manual way to

actually verify one of our contracts on

the blockchain we learned a lot here so

be absolutely sure to take a minute to

go on a walk go get a cup of coffee go

grab some ice cream go post on Twitter

that that you've taken an extra step in

your web 3 developer Journey you should

be incredibly proud of yourself for

getting this far like I said earlier

installing some of these tools like vs

code and Foundry can be one of the

hardest parts of this entire course so

if you're in here if you're working with

me you're doing fantastic we've got a

lot more to go but just by getting this

far you've done incredibly well so with

that being said take that break remember

breakes are good for your brain take

that break and we'll see you in the next

one