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When it comes to use reducer we really need to understand one thing we cannot update state directly.

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Again let me repeat we are not allowed to update our state directly.

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You see so far in our app we followed this pattern.

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First we set up state.

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Then we add some state values using you state create some functions in the functions we use the set

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function that is returned return from your state and eventually will pass its functions down to components

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where users interact with our state by clicking the buttons for example.

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Now when it comes to user reducer in our functions we're not going to update our state using set functions.

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The second parameter from you state in fact use reducer returns a state and a dispatch function that

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is responsible for updating our state in a dispatch function.

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We are going to pass our actions and you can think of actions as what we would want to do.

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You want to show the model you're going to pass open modal action you want to remove the item from the

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card you're going to pass a remove action and hopefully you get the gist.

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Once we dispatch the action we're going to handle it in the reducer and register is nothing but a function

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that takes two arguments.

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State or you can also think of it as an old state and a action.

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Notice how we pass two arguments when setting up a user juicer.

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First is our register function and the second is initial state.

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So within the reducer we're going to check what type of action is this budget and based on that we're

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going to update our state accordingly.

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We always always return a new state from reducer.

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So essentially we cannot let me repeat we cannot mutate the old state.

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We need to return a new one.

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And once we do that becomes our new state even though updating our state this way requires a bit more

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setup.

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It also gives us more structure and provides more predictable state management.