All language subtitles for 020 Working with Multiple Slices_en

So we did now translate our Redux-only,

non-React example

where we also use the counter

to this React application

so that there we also manage this counter state with Redux.

And we actually do more than what we did initially

in this module when we just got started with Redux.

Now, in this starting project,

which I provided to you,

we got a couple of other components as well,

not just a counter.

We get a couple of other components as well

because there's more I wanna practice

and teach you when it comes to Redux.

And therefore, it's now time

to use some of these other components.

In the App.js file, in this App component,

let's now return more than just the counter.

Let's add a fragment imported from React.

This built-in Fragment component

so that we can have a couple of adjacent JSX element

and let's also add our Header component here.

And for this, we need

to import Header from ./components/Header.

And let's also add the Auth component here.

And for this import Auth from ./components/Auth.

Now, if we do that,

we have this little demo application.

We still have the counter down there

and we could also remove it,

it's not related to this mini demo at all.

But I will leave it there

so that we still have the Redux state

for the counter and now we're also going to add state

for this demo application but which state?

Well, here I would like to make this login form work.

Not really, we won't really add authentication here.

We do this in a separate course section

because there's more to it than a little bit of Redux usage

but I wanna make sure that when we click Login,

we do switch into some login mode

and for example, what we see here

in the navigation bar changes.

These items and the logout button

should only be displayed if we are logged in in Redux

and I also wanna swap this login field here,

this login form for another component,

the UserProfile component which has some dummy output.

So we have a brand new state to manage.

And unlike the counter state,

which was just a basic example,

the authentication state

and the answer to the question

whether the user is logged in or not

is indeed not just local state,

which matters to one specific component

but it is application-wide state,

which matters to a lot of components in the application.

It matters to the Header,

it matters to the Auth component,

it matters to the UserProfile component in the end.

So therefore, this is the user authenticated state

is a perfect example for a state

that we could manage with React context

or since this section is about Redux, with Redux.

And that's therefore what I wanna do now.

I wanna make sure that when we click the Login button,

we set the user to authenticated.

If we click the Logout button,

I wanna set the user to not authenticated.

And for this, in our store here,

we can add a brand new state,

a brand new piece of data.

Now, the question

is where we should add our authentication data.

We do have this slice, which we created here,

this counter slice

and in there, we manage the counter

and the showCounter state.

We could, of course, also add a new property

to our state here.

Let's say the isAuthenticated property

and set this to false

and then add a new reducer, login, for example,

a new reducer method,

and in here, we then set is isAuthenticated to true.

We could do this

but logically it makes no sense.

The authentication status has nothing

to do with the counter.

Whilst it would technically work,

in programming we typically wanna separate our concerns.

We wanna make sure that this slice really focuses

on the counter-related state and actions.

And we should create a brand new slice

for the authentication state.

And that's, therefore, what I'll do.

I'll rename this initialState up here

to the initialCounterState

because we will soon have more than one initialState

and therefore, I set the initialState property in this slice

to the value stored in initialCounterState.

And then we can add a new slice

below the other slice,

though the exact position does not matter.

But we can call createSlice again

to create another slice

and this slice also, of course, needs an object

to be configured, just as our first slice.

This slice will be configured in exactly the same way

just with different values.

So we add a name here

and set this to auth, for example,

or authentication, whatever you want.

And we also wanna assign some initialState here.

Now, we could create this on the fly here

or again create a separate constant,

which holds this initial state

and that's what I'll do here.

I'll add a const initialAuthState,

which again let's say is an object

where we have the isAuthenticated property,

which initially is set to false.

And then here I set initialState equal

to this initialAuthState value.

And then we need to register our reducers.

These reducer methods, which can change this state.

And here I think two methods make sense.

A login method for well, logging the user in.

And a logout method for logging the user out.

In both methods, we'll receive the current state

as an argument automatically provided by Redux

and we can then mutate this state,

even though we technically shouldn't

but as I explained, we can do it here

because under the hood,

our code will be transformed to actually not mutate

the original state.

So it's safe to do that here.

And we can set state.isAuthenticated

equal to true here in the login state

and here in the logout state,

set isAuthenticated to false.

And that could be our slice for the auth part.

So I'll store this in a authSlice constant.

Up here we have the counterSlice,

now I have the authSlice as a second slice.

And now we wanna add that to our Redux store.

Now, very important,

when you work with multiple slices,

you still only have one Redux store,

so you still only call configureStore once.

This does not change.

And this store only has one root reducer here

but as I briefly explained earlier,

this reducer actually does not just take

a reducer function as an argument

but also an object which acts as a map of reducers

where you can then have any key names of your choice,

for example, counter

and then point at your different reducers.

Here, for example, add counterSlice.reduce.

And then we also add auth let's say as a key

and then here we add authSlice.reducer.

And these individual reducers here

will then automatically be merged together

into one main reducer,

which is exposed to this store.

That's how we can combine multiple slices

and their reducers.

Now, our authSlice, of course,

also exposes actions, which we can use

and therefore, I wanna expose those as well.

So export authActions,

which is authSlice.actions.

So now we added this authSlice.

Let's now use it in our different components

and of course, definitely feel free

to try this on your own first,

tap into the store and use the auth state

to conditionally show the Auth component

or the UserProfile component in App

and in the Header to conditionally show these items

or not show them.

And make sure that you dispatch the login

and logout actions in the appropriate places.

Just one important hint,

since we are merging our reducers together here,

the way we access data in our store changes slightly

and we will need to adjust this for the counter as well.

If we currently have a look at our application,

you see the counter is not being output down there

because we failed to extract it from the store.

In the Counter component, our code hasn't changed

but the code here changed.

All we have to do to make it work again

is go to our selectors,

so to use selector, and when we drill into our state

to read a value from there,

we now need to use these identifiers,

which we assigned in this reducer map

to drill into our specific state slices.

So for counter, I use counter as an identifier here,

hence in the Counter component,

when we wanna access the counter,

it's actually state.counter.counter.

This might look strange

but with the first .counter,

we make React Redux aware of the fact

that we wanna dive into this slice in the end,

into the state produced by this slicer's reducer

and then in that state slice,

we simply have a property named counter.

If that would be named differently,

if that would be value,

then in the Counter component,

it would be state.counter.value.

But since it isn't value but counter,

I'll revert it and revert it there as well

and that's why we have state.counter.counter.

And for showCounter, it's state.counter.showCounter.

So when you do try this on your own

for the authSlice, you should take this into account

when you read data from the store.

And with that, try it on your own.

We're going to do it together

in the next lecture.