All language subtitles for 5. [Dart] Functions - Part 1

Now in the last lesson, we covered flat buttons and the void callback that they expect.
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We also used the print function and gave it an input, or rather an argument.
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So in this lesson, I wants to quickly cover Dart functions.
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So if you already know what an argument is, what return does and what a function does, then feel free to
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skip this lesson and head over to the next one where we continue building out our Flutter app.
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But for those guys who are staying with me, functions as you can guess from the name, are there to give
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your app or you give your program some functionality, right? Now,
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in this lesson, I want to talk about functions in the most fundamental sense and when we using functions
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as programmers,
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fundamentally, we're trying to package bits of code together into a block and to call that block of code
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repeatedly, saving ourselves from typing the same code again and again and again.
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So for example, if you had a little housekeeping robot, this guy. His name is Bit Bob. And he does a number
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of things right?
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For example he'll go and get you milk every day. But you have to tell him how to do it.
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You have to tell him to leave the house, move right to blocks, move up four blocks, then move right to blocks,
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get the milk, come back. And you have to specify all these instructions to him because he's a robot and
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he doesn't understand contextual information like go to the store and get me some milk. Now if you had
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to do this day after day after day every single time you wanted milk, your fingers would start hurting,
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and you wouldn't want to keep typing out the same instructions.
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Right?
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So what can you do?
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Well we're programmers.
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We're born to be lazy.
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So what we can do instead, is we can take all these instructions that the robot understands, and we can
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package it into a block of code.
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Now a block of code, in many many programming languages, is represented by code that inside a set of curly
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braces.
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Once we've got all our instructions inside our curly braces, we can give that block of code a name.
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And in this case we've called it getMilk.
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Now every time I need some milk, I can tell the robot get milk and it'll know what to do because it
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will find this function called getMilk, and look inside it to see what it should do.
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It's almost like I'm creating a recipe, right?
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It's like, I want to eat cookies, but I don't want to bake cookies.
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So let me write down a recipe and give it to my housekeeping robot, so that they can make it for me.
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And that recipe or the name of the recipe is basically the name of our function. In Dart, the way that
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you would create the function looks like this.
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We've got the name of the function which is called getMilk, and then we've got the curly braces which
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enclose all of the things that should happen when this function gets called.
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And then later on when we actually need to use it, we will call the function or tell the computer to
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execute all of this by writing something like this, giving the name of the function.
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Now this is called a named function.
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Well it makes sense because it's got a name.
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Right?
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We can identify it by what it's called.
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Now if we dropped everything other than just the core parts, namely the parentheses and the curly braces
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and all the instructions, then this would become an anonymous function, because it doesn't have a name.
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Right?
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And these anonymous functions are legion.
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No just kidding.
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These are anonymous functions are actually very useful.
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They allow us to tell the computer to do something without explicitly having to create this entire function
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and give it a name and call its name. When we were coding up our onPressed which expected a void callback,
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it essentially wanted an anonymous function.
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We passed in the two empty parentheses, and we gave it the block of code that we want to be executed
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when the button got pressed. This is all you need to know about functions so far to be able to understand
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what's happening in our flat
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button. A little bit later on when we level up and we talk about functions in more detail, we'll talk
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more about what goes in these parentheses namely some inputs into the function. And also we'll talk about
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the return statement when we want our function to output something.
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But for now, just know that this is anonymous function.
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It has a set of parentheses and a set of curly braces. In the curly braces
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we say what should happen. So now that we're all caught up, in the next lesson we're gonna get back to
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coding up our dice app. And we're going to get our button to change our dice images to actually make the
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app work.
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So for all of that and more, I'll see on the next lesson.