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

我有一个非常具体的用例,我需要在dom中呈现一个类,然后设置另一个类。这就是我的解决方案,我发现它相当优雅。

const [value1, setValue1] = useState({value: 'whatever', onValue: false})


useEffect(() => {
    setValue1(prev => ({
      value: 'whatever',
      onValue: !prev.onValue, 
    }));
}, ['whatever'])

 
useEffect(() => {

// if you want to ensure the render happens before doThing2() then put it in a timeout of 1ms,
  setTimeout(doThing2, 1); 

// or if you are happy to call it immediately after setting value don't include the timeout
 doThing2()


}, [value1.onValue])

其他回答

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

我不认为用useRef区分挂载与否是一个好方法,不是一个更好的方法来确定useState()在useEffect()中生成的值是否为初始值?

const [val, setVal] = useState(null)

useEffect(() => {
  if (val === null) return
  console.log('not mounted, val updated', val)
}, [val])

UseEffect是主要的解决方案。但正如Darryl提到的,使用useEffect并将state作为第二个参数传入有一个缺陷,组件将在初始化过程中运行。如果你只想让回调函数使用更新后的状态值运行,你可以设置一个本地常量,并在setState和回调中使用它。

const [counter, setCounter] = useState(0);

const doSomething = () => {
  const updatedNumber = 123;
  setCounter(updatedNumber);

  // now you can "do something" with updatedNumber and don't have to worry about the async nature of setState!
  console.log(updatedNumber);
}

我认为你需要的是useState和useCallback:

useState react doc; useCallback react doc;

示例代码

import React, { useCallback, useState } from 'react';

const Test = () => {
  const [name, setName] = useState("");
  const testCallback = useCallback(() => console.log(name), [name]);

  return (
    <button onClick={() => {
      setName("Michael")
      testCallback();
    }}>Name</button>
  )
};

export default Test;

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];
};