javascript - 收到错误 : Argument of type '() => () => boolean' is not assignable to parameter of type 'EffectCallback'

Question

我是 typescript 的新手，当我尝试使用 useEffect 时出现错误在 typescript 中 react ，Argument of type '() => () => boolean' is not assignable to parameter of type 'EffectCallback'. ，任何人都可以帮助我为什么会收到这个错误？我在这里放了我的代码，任何帮助将不胜感激，

const useIsMounted = () => {
        const isMounted = React.useRef(false);
        React.useEffect(() => {
          isMounted.current = true;
          return () => isMounted.current = false;
        }, []);
        return isMounted;
    };

Answer 1

useEffect的功能( EffectCallback 类型)应该返回 void或 () => void | undefined .

function useEffect(effect: EffectCallback, deps?: DependencyList): void;

type EffectCallback = () => (void | (() => void | undefined));

在您的情况下，您返回 void => boolean :

// void => boolean
return () => (isMounted.current = false);

要修复它，请将范围添加到清理函数的语句中:

const useIsMounted = () => {
  const isMounted = React.useRef(false);
  React.useEffect(() => {
    isMounted.current = true;
    return () => {
      isMounted.current = false;
    };
  }, []);
  return isMounted;
};