Editing Openai/694590c5-f52c-800f-9af6-d10143a2d812 (section)

=== Assistant: Because reducers is for actions this slice CREATES, and extraReducers is for actions this slice REACTS TO but does NOT … ===
Because <code>reducers</code> is for actions this slice CREATES, and <code>extraReducers</code> is for actions this slice REACTS TO but does NOT own.

That’s not philosophy — it’s how RTK is designed.

==== <syntaxhighlight lang="ts">reducers: { ====
  userLoggedOut(state) {
    ...
  }
}

</syntaxhighlight>

This does two things at once:
# Creates an action creator ``<code>ts userLoggedOut() → { type: 'posts/userLoggedOut' } <syntaxhighlight>2. Registers a reducer for that action

So if you put logout logic in reducers of postsSlice, you are saying:

: 

That’s false.

==== </syntaxhighlight>ts ====
extraReducers: builder => {
  builder.addCase(userLoggedOut, ...)
}

<syntaxhighlight>
This does only one thing:
* Registers a reducer for an existing action
* Does NOT create an action creator

This is exactly what you want when:
* the action lives in another slice
* multiple slices must respond to one event
* you want one global event (auth/userLoggedOut)

==== If you put this in postsSlice.reducers: ====

</syntaxhighlight>ts
reducers: {
  userLoggedOut(state) {
    return initialState
  }
}

</code>``

Now you have:
* auth/userLoggedOut
* posts/userLoggedOut

Two different actions with the same name.

Result:
* dispatching auth/userLoggedOut ❌ does NOT clear posts
* dispatching posts/userLoggedOut ❌ does NOT log the user out

That’s a bug.

==== : ====

That’s it. No exceptions.