Handling Nested Async Calls in React with useEffect - Memory Leak Issue
I just started working with I'm trying to configure I'm facing a memory leak issue when using nested async calls inside a `useEffect` hook in my React component. The problem arises when I try to fetch user data based on a previously fetched list of user IDs. If the component unmounts before the fetch completes, I still see the warning about setting state on an unmounted component, which indicates that I may be leaking memory. Here's a simplified version of my code: ```javascript import React, { useEffect, useState } from 'react'; const UserList = () => { const [userIds, setUserIds] = useState([]); const [userDetails, setUserDetails] = useState([]); const [loading, setLoading] = useState(true); useEffect(() => { const fetchUserIds = async () => { const response = await fetch('https://api.example.com/userIds'); const data = await response.json(); setUserIds(data); }; fetchUserIds(); }, []); useEffect(() => { const fetchUserDetails = async () => { setLoading(true); const details = await Promise.all(userIds.map(async (id) => { const res = await fetch(`https://api.example.com/users/${id}`); return res.json(); })); setUserDetails(details); setLoading(false); }; if (userIds.length > 0) { fetchUserDetails(); } }, [userIds]); if (loading) return <div>Loading...</div>; return <div>{JSON.stringify(userDetails)}</div>; }; ``` I've tried adding a cleanup function to the `fetchUserDetails` function, but it seems like I'm not handling the promises correctly, leading to the warnings. Here's the cleanup code I attempted: ```javascript useEffect(() => { let isMounted = true; const fetchUserDetails = async () => { setLoading(true); const details = await Promise.all(userIds.map(async (id) => { const res = await fetch(`https://api.example.com/users/${id}`); return res.json(); })); if (isMounted) { setUserDetails(details); setLoading(false); } }; if (userIds.length > 0) { fetchUserDetails(); } return () => { isMounted = false; }; }, [userIds]); ``` While this approach seems logical, I still see warnings about state updates on unmounted components. I'm using React 17.0.2. Has anyone faced a similar issue, or can you suggest a better pattern to manage this kind of nested asynchronous workflow? Any help would be greatly appreciated! I'm working in a Debian environment. What's the correct way to implement this? I've been using Javascript for about a year now. I'm open to any suggestions.