All language subtitles for 016 Bonus_ Using useReducer()_en

Now as kind of a bonus,

you could say to this module

we can also practice working with useReducer again

because what did we learn about useReducer?

When does it shine or when is it worth considering using it?

We learned that it's great to use users, user

or that it's worth a thought to use useReducer

if we need more power.

So if you have a lot of different possible state values

and a lot of complex state updating logic

but also if we have related pieces of state

which are managed in individual states

especially if those states depend on each other.

Now, arguably, that's not really the case here.

We never have a lot of different state values

nor a very complex state updating logic here.

And in addition we do have multiple states

that kind of belong together

the value and the touch state.

They both kind of represent the state of the input element

but they don't really depend on each other.

That would not really be true to state this

nonetheless to practice working with useReducer again,

I will import useReducer here now instead of useState

and now use useReducer for

managing these two state pieces here.

But again, it's not strictly required

it's mainly another practice for useReducer.

So I'll start by adding a reducer function,

input, state reducer function we could say,

and you'll learn that this reducer function

takes two main arguments.

The previous state snapshot, which will be provided

and passed in automatically by React

and an action which will also be passed

into this function automatically by React.

But which is the action you dispatched somewhere

in your code.

And then ultimately you have

to return a new state snapshot here,

and we can return a default state snapshot

which we always return unless we change it in code

we're about to add, and that could contain our value.

So the value for this input

which initially is an empty string

and the is touched state,

which initially is false.

And then here in the use input hook,

we can call useReducer

and pass our input state reducer function to useReducer

and also provide our initial state

which is basically this state here

and hence I'll add the number of constant

initial input state

which simply holds this object.

And I returned this object here

and I also set this here as an initial state.

So the initial input state.

Now useReducer as you learned returns an array

with exactly two elements, just like useState.

And the first element is always the state managed

by the reducer.

So the input state as we could call it.

And the second element is always a dispatched function

which allows you to dispatch actions against that reducer.

So I'll name it dispatch,

but you can of course pick any name you want here.

Now we can get rid of these two states license here now,

and now instead start working with input state and dispatch.

For example, here for validating the value there

we can now use input state dot value.

We know that our input state will have a value property

because that is the structure our state here will have

the state managed by this reducer.

We can also get the touch state from there

input state is touched.

Now when value change handler executes

we wanna dispatch an action against our reducer

and you learn that it's totally up to you

how is such an actual looks like, but it often is an object

with a type property which identifies the action

and here I'll sets type to a string called input

and it can also carry a payload.

And here I'll add a value property to this object

which holds event target value as a value.

And then I can get rid of this line here,

where we set, entered to value.

Now we also wanna dispatch in the end input blur handler

and there we could use the identifier blur

and we can also provide a value here

but we're not actually interested in the value here.

So there instead,

I can also just pass in an action like this.

Now, when we reset

we can dispatch an object where to type is reset.

For example, now when we return,

I wanna return the value

and that would be input state dot value

and data's already it with that we're good here.

So now we just need to handle these free action types

input blur and reset in this reducer.

So we can check if action dot type is equal to input

or if action type is equal to blur

or if action type is equal to reset.

Now, if it is equal to input then

I wanna return a new state object

where I in the end

set value to action dot value

because in the input action case here,

we will have a value property on the action object,

which carries the entered value.

And I wanna set the state.

Now I don't wanna set is touched to true

because whilst we have a keystroke

the user didn't finish typing yet.

So I don't wanna set is touched to true

otherwise we would kind of break to

behavior rebuilt over this module

where we only present error messages

once the user is really done,

hence here, instead I wanna copy the existing state.

So I will set is touched here to state dot is touched

using the previous states is touched value.

Now in the blur case I wanna return a new object as well.

And here I wanna set is touched to true

because that is what we do when the input blurs

it should now be marked as touched

on the other hand here I don't care about the value

we could update it.

We could get it from this event object in

the input blur handler

but we don't really need to do that

since we're updating the value on every keystroke anyways.

So hence here I can set value to state dot value

simply using the existing value.

And if we reset,

I return an object where I said is attached to false

and value back to an empty string to reset this.

And this is now our custom hook using useReducer.

If you now check does again here

you still get the same behavior as before

where we can fill out the form to make it work

and where we still also get errors, if we will have errors.

So that all still works as before.

But now with the useReducer simply as

a little extra exercise.