在我的例子中，问题是父组件隐藏了子组件，因为子组件中的条件发生了变化。

我所做的就是改变条件，让子组件总是显示出来。

发生了什么事:

const ParentComponent:FC = () => {
  ...
  if (someCondition) {
    return null;
  }

  return (
   <>
     Some cool text here
    
     <ChildModalComponent message="this is a cool modal" />
   </>
  )
}



const ChildModalComponent: FC = () => {
  ...
  const handleSubmit = () => {
    setSomeCondition(true);
  }
}

因此，在点击提交后，由于父条件(someCondition)，模式被自动隐藏。

我是怎么解决的?

我改变了父组件中someCondition检查的位置，所以子组件总是显示:

const ParentComponent:FC = () => {
  ...
  return (
   <>
     {!someCondition && <>Some cool text here</>
    
     <ChildModalComponent message="this is a cool modal" />
   </>
  )
}

取决于你如何打开你的网页，你可能不会引起挂载。例如使用<Link/>返回到已经挂载在虚拟DOM中的页面，因此需要componentDidMount生命周期中的数据。

我通过提供useEffect钩子中使用的所有参数来解决这个问题

代码报告了该错误:

useEffect(() => {
    getDistrict({
      geonameid: countryId,
      subdistrict: level,
    }).then((res) => {
      ......
    });
  }, [countryId]);

修复后的代码:

useEffect(() => {
    getDistrict({
      geonameid: countryId,
      subdistrict: level,
    }).then((res) => {
      ......
    });
  }, [countryId,level]);

可以看到，问题解决后，我提供了所有的参数(包括水平参数)，应该通过。

这是一个React挂钩的具体解决方案

错误

警告:无法对未挂载的组件执行React状态更新。

解决方案

您可以在useEffect内部声明let isMounted = true，一旦组件被卸载，它将在清理回调中被更改。在状态更新之前，你现在有条件地检查这个变量:

useEffect(() => {
  let isMounted = true;               // note mutable flag
  someAsyncOperation().then(data => {
    if (isMounted) setState(data);    // add conditional check
  })
  return () => { isMounted = false }; // cleanup toggles value, if unmounted
}, []);                               // adjust dependencies to your needs

const Parent = () => { const [mounted, setMounted] = useState(true); return ( <div> Parent: <button onClick={() => setMounted(!mounted)}> {mounted ? "Unmount" : "Mount"} Child </button> {mounted && <Child />} <p> Unmount Child, while it is still loading. It won't set state later on, so no error is triggered. </p> </div> ); }; const Child = () => { const [state, setState] = useState("loading (4 sec)..."); useEffect(() => { let isMounted = true; fetchData(); return () => { isMounted = false; }; // simulate some Web API fetching function fetchData() { setTimeout(() => { // drop "if (isMounted)" to trigger error again // (take IDE, doesn't work with stack snippet) if (isMounted) setState("data fetched") else console.log("aborted setState on unmounted component") }, 4000); } }, []); return <div>Child: {state}</div>; }; ReactDOM.render(<Parent />, document.getElementById("root")); <script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.0/umd/react.production.min.js" integrity="sha256-32Gmw5rBDXyMjg/73FgpukoTZdMrxuYW7tj8adbN8z4=" crossorigin="anonymous"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.0/umd/react-dom.production.min.js" integrity="sha256-bjQ42ac3EN0GqK40pC9gGi/YixvKyZ24qMP/9HiGW7w=" crossorigin="anonymous"></script> <div id="root"></div> <script>var { useReducer, useEffect, useState, useRef } = React</script>

扩展:自定义useAsync钩子

我们可以将所有样板包封装到一个自定义Hook中，当组件卸载或依赖值之前发生更改时，该Hook会自动中止异步函数:

function useAsync(asyncFn, onSuccess) {
  useEffect(() => {
    let isActive = true;
    asyncFn().then(data => {
      if (isActive) onSuccess(data);
    });
    return () => { isActive = false };
  }, [asyncFn, onSuccess]);
}

// custom Hook for automatic abortion on unmount or dependency change // You might add onFailure for promise errors as well. function useAsync(asyncFn, onSuccess) { useEffect(() => { let isActive = true; asyncFn().then(data => { if (isActive) onSuccess(data) else console.log("aborted setState on unmounted component") }); return () => { isActive = false; }; }, [asyncFn, onSuccess]); } const Child = () => { const [state, setState] = useState("loading (4 sec)..."); useAsync(simulateFetchData, setState); return <div>Child: {state}</div>; }; const Parent = () => { const [mounted, setMounted] = useState(true); return ( <div> Parent: <button onClick={() => setMounted(!mounted)}> {mounted ? "Unmount" : "Mount"} Child </button> {mounted && <Child />} <p> Unmount Child, while it is still loading. It won't set state later on, so no error is triggered. </p> </div> ); }; const simulateFetchData = () => new Promise( resolve => setTimeout(() => resolve("data fetched"), 4000)); ReactDOM.render(<Parent />, document.getElementById("root")); <script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.13.0/umd/react.production.min.js" integrity="sha256-32Gmw5rBDXyMjg/73FgpukoTZdMrxuYW7tj8adbN8z4=" crossorigin="anonymous"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.13.0/umd/react-dom.production.min.js" integrity="sha256-bjQ42ac3EN0GqK40pC9gGi/YixvKyZ24qMP/9HiGW7w=" crossorigin="anonymous"></script> <div id="root"></div> <script>var { useReducer, useEffect, useState, useRef } = React</script>

更多关于效果清理:过度反应:使用效果的完整指南

对于这个错误，我有两个解决方案:

返回:

如果你使用了钩子和useEffect，那么使用一个useEffect的返回结束。

useEffect(() => {
    window.addEventListener('mousemove', logMouseMove)
    return () => {
        window.removeEventListener('mousemove', logMouseMove)
    }
}, [])

componentWillUnmount:

如果你使用componentDidMount，那么把componentWillUnmount放在它旁边。

componentDidMount() { 
    window.addEventListener('mousemove', this.logMouseMove)
}

componentWillUnmount() {
    window.removeEventListener('mousemove', this.logMouseMove)
}

受@ford04 answer的启发，我使用了这个钩子，它也接受success, errors, finally和abortFn的回调:

export const useAsync = (
        asyncFn, 
        onSuccess = false, 
        onError = false, 
        onFinally = false, 
        abortFn = false
    ) => {

    useEffect(() => {
        let isMounted = true;
        const run = async () => {
            try{
                let data = await asyncFn()
                if (isMounted && onSuccess) onSuccess(data)
            } catch(error) {
                if (isMounted && onError) onSuccess(error)
            } finally {
                if (isMounted && onFinally) onFinally()
            }
        }
        run()
        return () => {
            if(abortFn) abortFn()
            isMounted = false
        };
    }, [asyncFn, onSuccess])
}

如果asyncFn正在从后端进行某种类型的读取，那么在组件卸载时中止它通常是有意义的(尽管并非总是如此，有时如果ie。你正在加载一些数据到存储中，你可能只是想要完成它，即使组件是unmounted)