Is there a way to access global state in createSlice?

Question

Here is an example:

const user = createSlice({
  name: 'user',
  initialState: { name: '', age: 20 },
  reducers: {
    setUserName: (state, action) => {
      state.name = action.payload // mutate the state all you want with immer
    }
  },
  // "map object API"
  extraReducers: {
    [counter.actions.increment]: (state, action) => {
      state.age += 1
    }
  }
})

Can I get access to the counter state? Let's say I want to increment age only when the counter is 30. Otherwise, I would need to listen when the count is changing in useEffect hook and dispatch some action that will handle age increment (?).

In other words, what's the best way to compute the slice of state based on the current global state using redux-toolkit?

Answer 1

This is covered in the Redux FAQ entry on sharing state between reducers.

Pasting the key points:

• If a reducer needs to know data from another slice of state, the state tree shape may need to be reorganized so that a single reducer is handling more of the data.
• You may need to write some custom functions for handling some of these actions. This may require replacing combineReducers with your own top-level reducer function. You can also use a utility such as reduce-reducers to run combineReducers to handle most actions, but also run a more specialized reducer for specific actions that cross state slices.
• Async action creators such as redux-thunk have access to the entire state through getState(). An action creator can retrieve additional data from the state and put it in an action, so that each reducer has enough information to update its own state slice.