Handling Nested State Updates in React with useReducer and useEffect
I've been banging my head against this for hours. After trying multiple solutions online, I still can't figure this out. I'm having trouble managing nested state updates in my React application using `useReducer` and `useEffect`. I have a state that looks like this: ```javascript const initialState = { user: { name: '', age: null, preferences: {} } }; function reducer(state, action) { switch (action.type) { case 'UPDATE_NAME': return {...state, user: {...state.user, name: action.payload}}; case 'UPDATE_PREFERENCES': return {...state, user: {...state.user, preferences: {...state.user.preferences, ...action.payload}}}; default: return state; } } const [state, dispatch] = useReducer(reducer, initialState); ``` In my component, I have a `useEffect` that is supposed to update the preferences based on a prop that comes in: ```javascript useEffect(() => { if (incomingPreferences) { dispatch({ type: 'UPDATE_PREFERENCES', payload: incomingPreferences }); } }, [incomingPreferences]); ``` The scenario arises when the `incomingPreferences` prop changes frequently. Sometimes the state doesn't seem to update properly, and I see stale values in the `preferences` object. I tried adding a console log in the `useEffect` to see the value of `incomingPreferences`, and it logs the expected values, but the state does not reflect this change consistently. I also checked that the component is re-rendering by logging the state after each dispatch: ```javascript useEffect(() => { console.log('Updated state:', state); }, [state]); ``` I'm seeing the old values of `preferences` more often than not, which leads me to suspect that the way I'm merging the state is not working as I intended. Has anyone encountered a similar scenario, or does anyone have suggestions on how to ensure the state updates correctly for nested objects when using `useReducer`? Iām using React 17.0.2. My development environment is macOS.