Warning:useEffect函数中取消所有订阅和异步任务_to fix, cancel all subscriptions and asynchronous -优快云博客

Warning：Can’t perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.useEffect清理函数中取消所有订阅和异步任务

报错：

react-dom.development.js:88 Warning: 
Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.
    in ReportMng
    in Unknown (created by Context.Consumer)

翻译一下：

无法对已卸载的组件执行React状态更新。这是一个no-op，但它表明应用程序中存在内存泄漏。若要修复，请在useEffect清理函数中取消所有订阅和异步任务。

看下源码中报错的位置：

原因：

组件卸载了，但是仍处于渲染数据状态（如：setState，useState），一般写定时器时候会有出现。其他情况也会，只要组件卸载但仍在更新数据时机

解决如下：

这个错误不大会影响实际使用，解决非常简单。

先讲下hook函数组件的解决：

第一种定时器情况：

const [update, setUpdate] = useState(1);
 useEffect(() => {
    const creatInt = setInterval(() => {    //假设这里写了定时器来更新update
      setUpdate(c => c + 1);
    }, 2000);
return () => {
      clearInterval(creatInt);   //（重点）这里清除掉定时器  
    };
  }, []);

第二种useSate情况：

  useEffect(() => {
    let isUnmount = false;      //这里插入isUnmount
    const fetchDetail = async () => {
      const res = await getDetail(detailId);
      if (res.code === 0 && !isUnmount) {  //加上判断isUnmount才去更新数据渲染组件
        setDetail(res.data);
      }
    };
    fetchDetail();
    return () => isUnmount = true;   //最好return一个isUnmount
  }, [detail]);

改成这个后warning消失

// const mountedRef = useRef(true); // useEffect清理函数中取消所有订阅和异步任务
  let isUnmount = false; //这里插入isUnmount
  useEffect(() => {
    // if (!permission?.writeAuth) {
    //   window.location.href = `/admin/forbidden?url=${encodeURI(window.location.href)}`;
    // }
    getCityList();

    return () => isUnmount = true; //最好return一个isUnmount
    // mountedRef.current = false;
  }, []);
  // 获取城市列表
  const getCityList = useCallback(async (params: GetAuthCityListResponse) => {
    const res = await getAuthCityList(params);
    if (res?.code === 0 && !isUnmount) {
      // if (!mountedRef.current) return null;
      setCityIdOptions(res?.data);
      console.log('11111', !isNotCreate);
      if (!isNotCreate) {
        getAppealDetails();
      }
    }
  }, []);
  // 查询详情
  const getAppealDetails = useCallback(async () => {}, []);