反应useEffect比较对象

问题描述

我正在使用react useEffect 钩子，并检查对象是否已更改，然后才再次运行该钩子.

I am using react useEffect hooks and checking if an object has changed and only then run the hook again.

我的代码如下.

const useExample = (apiOptions) => {
    const [data, updateData] = useState([]);
    useEffect(() => {
       const [data, updateData] = useState<any>([]);
        doSomethingCool(apiOptions).then(res => {
           updateData(response.data);
       })
    }, [apiOptions]);

    return {
        data
    };
};

不幸的是，由于无法识别出相同的对象，它一直在运行.

Unfortunately it keeps running as the objects are not being recognised as being the same.

我相信以下是一个示例.

I believe the following is an example of why.

const objA = {
   method: 'GET'
}

const objB = {
   method: 'GET'
}

console.log(objA === objB)

也许运行 JSON.stringify(apiOptions)可行吗?

推荐答案

使用 apiOptions 作为状态值

我不确定您如何使用自定义钩子，但是通过使用 useState 将 apiOptions 设置为状态值应该可以正常工作.这样，您可以将其作为状态值提供给自定义钩子，如下所示:

Use apiOptions as state value

I'm not sure how you are consuming the custom hook but making apiOptions a state value by using useState should work just fine. This way you can serve it to your custom hook as a state value like so:

const [apiOptions, setApiOptions] = useState({ a: 1 })
const { data } = useExample(apiOptions)

这样，仅当您使用 setApiOptions 时，它才会更改.

This way it's going to change only when you use setApiOptions.

示例1

import { useState, useEffect } from 'react';

const useExample = (apiOptions) => {
  const [data, updateData] = useState([]);

  useEffect(() => {
    console.log('effect triggered')
  }, [apiOptions]);

  return {
    data
  };
}
export default function App() {
  const [apiOptions, setApiOptions] = useState({ a: 1 })
  const { data } = useExample(apiOptions);
  const [somethingElse, setSomethingElse] = useState('default state')

  return <div>
    <button onClick={() => { setApiOptions({ a: 1 }) }}>change apiOptions</button>
    <button onClick={() => { setSomethingElse('state') }}>
      change something else to force rerender
    </button>
  </div>;
}

您可以按照此处:

function deepCompareEquals(a, b){
  // TODO: implement deep comparison here
  // something like lodash
  // return _.isEqual(a, b);
}

function useDeepCompareMemoize(value) {
  const ref = useRef()
  // it can be done by using useMemo as well
  // but useRef is rather cleaner and easier

  if (!deepCompareEquals(value, ref.current)) {
    ref.current = value
  }

  return ref.current
}

function useDeepCompareEffect(callback, dependencies) {
  useEffect(
    callback,
    dependencies.map(useDeepCompareMemoize)
  )
}

您可以像使用 useEffect 一样使用它.

You can use it like you'd use useEffect.

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