React useCallback 内存泄漏卸载组件

Question

我是 React 的新手，我收到此错误：

警告：无法对卸载的组件执行 React 状态更新。这是一个空操作，但它表明您的应用程序中存在内存泄漏。要修复，请取消 useEffect 清理函数中的所有订阅和异步任务。

据我了解，似乎我有内存泄漏并且需要对 useCallback 钩子进行 useEffect 清理？

我尝试添加一个useRef来检查安装，但返回不会将状态更改为 false。

const MyComponent = ({data}) => {
  const mounted = useRef(true);
  const [loading, setLoading] = useState(false);

  const isLoading = useCallback(async () => {
    setLoading(true);

    if (data) {
      console.log('YAY DATA: ', data);
    }

    return () => {
      setLoading(false); // unreachable code
      mounted.current = false; // does this do the cleanup?
    };
  }, [loading]);

  return (
    //...some component
  );
};

export default MyComponent;

Answer 1

如果您执行的异步操作在完成时需要为状态设置某些内容，则必须确保在更新状态之前组件仍处于挂载状态。

为此，您可以这样做：

const MyComponent = (props) => {
  const mounted = useRef(false);

  useEffect(() => {
        mounted.current = true; // Will set it to true on mount ...
        return () => { mounted.current = false; }; // ... and to false on unmount
  }, []);

  const [loading, setLoading] = useState(false);
  const [data, setData] = useState([]);

  const myAsyncCallback = useCallback(async () => {
    setLoading(true);

    // Await for an async function...
    const data = await yourAsyncFunction(...); // Complete with proper code here

    // While waiting for yourAsyncFunction to be done,
    // It's possible that your component had been unmounted.

    // Therefore, you have to check if the component is still mounted before updating states
    if (mounted.current) { 
      setLoading(false);
      setData(data);
    }
  }, []);

  return (
    //...some component that calls myAsyncCallback
  );
};

export default MyComponent;