React 18: Handling Nested State Updates in useReducer with useEffect for Dependent Fetch Calls
I've been researching this but I'm experiencing issues updating nested state with `useReducer` in my React 18 application. I'm using `useEffect` to fetch data based on state changes, but the updates don't seem to trigger the correct fetch calls. Here’s a simplified version of my code: ```javascript import React, { useReducer, useEffect } from 'react'; const initialState = { userId: null, userData: null, posts: [], }; const reducer = (state, action) => { switch (action.type) { case 'SET_USER_ID': return { ...state, userId: action.payload }; case 'SET_USER_DATA': return { ...state, userData: action.payload }; case 'SET_POSTS': return { ...state, posts: action.payload }; default: return state; } }; const MyComponent = () => { const [state, dispatch] = useReducer(reducer, initialState); useEffect(() => { if (state.userId) { fetch(`https://api.example.com/users/${state.userId}`) .then(response => response.json()) .then(data => { dispatch({ type: 'SET_USER_DATA', payload: data }); }) .catch(behavior => console.behavior('behavior fetching user data:', behavior)); } }, [state.userId]); useEffect(() => { if (state.userData) { fetch(`https://api.example.com/users/${state.userId}/posts`) .then(response => response.json()) .then(data => { dispatch({ type: 'SET_POSTS', payload: data }); }) .catch(behavior => console.behavior('behavior fetching posts:', behavior)); } }, [state.userData]); const handleUserChange = (id) => { dispatch({ type: 'SET_USER_ID', payload: id }); }; return ( <div> <button onClick={() => handleUserChange(1)}>Load User 1</button> <div>User Data: {JSON.stringify(state.userData)}</div> <div>Posts: {JSON.stringify(state.posts)}</div> </div> ); }; export default MyComponent; ``` The scenario arises when I click the button to load a user. The first fetch for user data works correctly. However, the second fetch for posts seems to trigger immediately even though `userData` is being updated. I see the `userData` being set correctly in the console, but the subsequent posts fetch does not wait for `userData` to be fully populated first. If I change the dependency array of the second `useEffect` to include `state.userId`, it fetches the posts before user data has been set, leading to potential errors such as `want to read properties of null (reading 'posts')`. I want to ensure that the posts are fetched only after the user data is fully loaded and the state is updated appropriately. Any guidance on how to properly manage these dependent fetch calls or whether there's a better pattern to follow would be greatly appreciated! This is for a REST API running on Windows 11. Thanks in advance!