React钩子引入了useState来设置组件状态。但是我如何使用钩子来替换下面的回调代码:

setState(
  { name: "Michael" },
  () => console.log(this.state)
);

我想在状态更新后做一些事情。

我知道我可以使用useEffect来做额外的事情,但我必须检查之前的状态值,这需要位代码。我正在寻找一个简单的解决方案,可以使用useState挂钩。


当前回答

简单的解决方案,只需安装

我使用-state-with-callback

import React from 'react';
import { useStateWithCallbackLazy } from "use-state-with-callback";

const initialFilters = {
  smart_filter: "",
};

const MyCallBackComp = () => {
  const [filters, setFilters] = useStateWithCallbackLazy(initialFilters);

  const filterSearchHandle = (e) => {
    setFilters(
      {
        ...filters,
        smart_filter: e,
      },
      (value) => console.log("smartFilters:>", value)
    );
  };

  return (
    <Input
      type="text"
      onChange={(e) => filterSearchHandle(e.target.value)}
      name="filter"
      placeholder="Search any thing..."
    />
  );
};

认为: 反应usestate回调

其他回答

我认为,使用useEffect不是一种直观的方式。

我为此创建了一个包装器。在这个自定义钩子中,你可以将你的回调传递给setState参数,而不是useState参数。

我刚刚创建了Typescript版本。所以如果你需要在Javascript中使用它,只需从代码中删除一些类型符号。

使用

const [state, setState] = useStateCallback(1);
setState(2, (n) => {
  console.log(n) // 2
});

宣言

import { SetStateAction, useCallback, useEffect, useRef, useState } from 'react';

type Callback<T> = (value?: T) => void;
type DispatchWithCallback<T> = (value: T, callback?: Callback<T>) => void;

function useStateCallback<T>(initialState: T | (() => T)): [T, DispatchWithCallback<SetStateAction<T>>] {
  const [state, _setState] = useState(initialState);

  const callbackRef = useRef<Callback<T>>();
  const isFirstCallbackCall = useRef<boolean>(true);

  const setState = useCallback((setStateAction: SetStateAction<T>, callback?: Callback<T>): void => {
    callbackRef.current = callback;
    _setState(setStateAction);
  }, []);

  useEffect(() => {
    if (isFirstCallbackCall.current) {
      isFirstCallbackCall.current = false;
      return;
    }
    callbackRef.current?.(state);
  }, [state]);

  return [state, setState];
}

export default useStateCallback;

缺点

如果传递的箭头函数引用了一个变量外部函数,那么它将捕获当前值,而不是状态更新后的值。 在上面的使用示例中,console.log(state)将打印1而不是2。

你可以使用以下方法,我知道获得更新后的最新状态:

useEffect https://reactjs.org/docs/hooks-reference.html#useeffect

    const [state, setState] = useState({name: "Michael"});
    
    const handleChangeName = () => {
      setState({name: "Jack"});
    }
    
    useEffect(() => {
      console.log(state.name); //"Jack"

      //do something here
    }, [state]);

功能更新 https://reactjs.org/docs/hooks-reference.html#functional-updates 如果新的状态是用之前的状态计算出来的,你可以传递一个函数给setState。该函数将接收之前的值,并返回更新后的值。”

    const [state, setState] = useState({name: "Michael"});

    const handleChangeName = () => {
      setState({name: "Jack"})
      setState(prevState => {
        console.log(prevState.name);//"Jack"

        //do something here

        // return updated state
        return prevState;
      });
    }

useRef https://reactjs.org/docs/hooks-reference.html#useref 返回的ref对象将在组件的整个生命周期内持续存在。

    const [state, setState] = useState({name: "Michael"});

    const stateRef = useRef(state);
    stateRef.current  = state;
    const handleClick = () => {
      setState({name: "Jack"});

      setTimeout(() => {
        //it refers to old state object
        console.log(state.name);// "Michael";

        //out of syntheticEvent and after batch update
        console.log(stateRef.current.name);//"Jack"

        //do something here
      }, 0);
    }

在react synticevent处理程序中,setState是一个批量更新过程,因此每次状态更改都会等待并返回一个新状态。 setState()并不总是立即更新组件。它可以批处理或延迟更新。", https://reactjs.org/docs/react-component.html#setstate

这里有一个有用的链接 React是否保持状态更新的顺序?

我有一个用例,我想做一个api调用与一些参数后的状态设置。我不想设置这些参数作为我的状态,所以我做了一个自定义钩子,这是我的解决方案

import { useState, useCallback, useRef, useEffect } from 'react';
import _isFunction from 'lodash/isFunction';
import _noop from 'lodash/noop';

export const useStateWithCallback = initialState => {
  const [state, setState] = useState(initialState);
  const callbackRef = useRef(_noop);

  const handleStateChange = useCallback((updatedState, callback) => {
    setState(updatedState);
    if (_isFunction(callback)) callbackRef.current = callback;
  }, []);

  useEffect(() => {
    callbackRef.current();
    callbackRef.current = _noop; // to clear the callback after it is executed
  }, [state]);

  return [state, handleStateChange];
};

我探索了use-state with-callback npm库和其他类似的自定义钩子,但最后我意识到我可以做这样的事情:

const [user, setUser] = React.useState(
  {firstName: 'joe', lastName: 'schmo'}
)

const handleFirstNameChange=(val)=> {
  const updatedUser = {
     ...user,
     firstName: val
  }
  setUser(updatedUser)
  updateDatabase(updatedUser)
}

用useEffect模拟setState回调,只在状态更新时触发(不是初始状态):

const [state, setState] = useState({ name: "Michael" })
const isFirstRender = useRef(true)
useEffect(() => {
  if (isFirstRender.current) {
    isFirstRender.current = false // toggle flag after first render/mounting
    return;
  }
  console.log(state) // do something after state has updated
}, [state])

自定义钩子useEffectUpdate

function useEffectUpdate(callback) {
  const isFirstRender = useRef(true);
  useEffect(() => {
    if (isFirstRender.current) {
      isFirstRender.current = false; // toggle flag after first render/mounting
      return;
    }
    callback(); // performing action after state has updated
  }, [callback]);
}

// client usage, given some state dep
const cb = useCallback(() => { console.log(state) }, [state]); // memoize callback
useEffectUpdate(cb);