React.createRef()，React.forwardRef()，forwardRef()结合next.js的link进行路由跳转

码云https://gitee.com/skyvilm/react-next.js

1.React.createRef()

作用：获取dom元素

使用

import React,{Component} from 'react'

export default class Index extends Componen{

constructor(props){

super(props)

this.myref=React.createRef(); //创建节点

}

componentDidMount(){

this.myref.current； //节点，React.createRef()会返回一个current对象，密闭性的

}

render(){

return <div ref={this.father}>

this is div

</div>

}

源码：

import type {RefObject} from 'shared/ReactTypes';//可修改value的不可变的对象export function createRef(): RefObject {

//初始化ref对象，属性current初始值为null const refObject = {

current: null,

};

if (DEV) {

Object.seal(refObject); //表示密闭性，不可删除属性

}

return refObject;

}

2.React.forwardRef()

作用：

React.forwardRef 会创建一个React组件，这个组件能够将其接受的 ref 属性转发到其组件树下的另一个组件中；

使用：

import React from 'react'//funciton component是没有dom实例的，因为它是PureComponent，所以没有this，// 所以不能通过createRef()来拿到实例//将Father的father传给子组件，并绑定子组件的DOM实例，从而能在父组件拿到子组件的DOM实例const Child=React.forwardRef((props,ref)=>{

return <div ref={ref}>child div</div>

})export default class Index extends Componen{

constructor(props){

super(props)

this.father=React.createRef()

}

componentDidMount(){

this.father.current.value='test' }

render(){

return <Child ref={this.father} />

}

源码：

import warningWithoutStack from 'shared/warningWithoutStack';export default function forwardRef<Props, ElementType: React$ElementType>(

render: (props: Props, ref: React $Ref\) =\> React$ Node,

) {

//__DEV__可不看 if (DEV) {

if (render != null && render.$$typeof === REACT_MEMO_TYPE) {

warningWithoutStack(

false,

'forwardRef requires a render function but received a `memo` ' +

'component. Instead of forwardRef(memo(...)), use ' +

'memo(forwardRef(...)).',

);

} else if (typeof render !== 'function') {

warningWithoutStack(

false,

'forwardRef requires a render function but was given %s.',

render === null ? 'null' : typeof render,

);

} else {

warningWithoutStack(

// Do not warn for 0 arguments because it could be due to usage of the 'arguments' object render.length === 0 || render.length === 2,

'forwardRef render functions accept exactly two parameters: props and ref. %s',

render.length === 1 ? 'Did you forget to use the ref parameter?' : 'Any additional parameter will be undefined.',

);

}

if (render != null) {

warningWithoutStack(

render.defaultProps == null && render.propTypes == null,

'forwardRef render functions do not support propTypes or defaultProps. ' +

'Did you accidentally pass a React component?',

);

}

return {

//被forwardRef包裹后，组件内部的$$typeof是REACT_FORWARD_REF_TYPE $$typeof: REACT_FORWARD_REF_TYPE,

//render即包装的FunctionComponent，ClassComponent是不用forwardRef的 render,

};

}

解析：

不看__DEV__的话，返回的也是一个Object，也就是说，Child被forwardRef包裹后，React.forwardRef(Child)的$$typeof是REACT_FORWARD_REF_TYPE

注意：

一旦在Father组件中，用JSX引用了Child组件，那么就是React.createElement(React.forwardRef(Child))，又包裹了一层，此时的$$typeof`是`REACT_ELEMENT_TYPE`，`type`是`React.forwardRef(Child)`，`type`里面的`$$typeof是REACT_FORWARD_REF_TYPE

3.React.forwardRef()结合next.js的link进行路由跳转

import React, { Component } from 'react';

import Link from 'next/link';

import Router from "next/router";

const RedLink=React.forwardRef((props,ref)=>{

return (

)

})

class index extends Component {

render() {

return (

<div>

<h2>子集是组件的跳转，</h2>

<small>不知道为什么只能用a</small>

</Link>

</div>

);

}

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