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父组件

1) ref必须传值, 否则childRef拿不到子组件的数据和方法

注意: 不一定使用app组件, 其他的任何父组件都可以

import "./App.css";
import React, { useEffect, useRef } from "react";
import RefToGetChild from "./components/RefToGetChild";
import _ from 'lodash';const App: React.FC = () => {const childRef = useRef<any>(null);useEffect(() => {console.log(_.get(childRef, 'current'));}, [_.get(childRef, 'current')]);return (<div><RefToGetChild ref={childRef} message={"子组件: say hello"} /><button onClick={() => {const child = _.get(childRef, 'current');const buttonDom = child.buttonRef.currentbuttonDom?.click();}}>父组件: trigger child button</button><button onClick={() => {const child = _.get(childRef, 'current');child?.onTest();}}>父组件: 使用子组件的onTest方法</button><div>父组件: 子组件的data {JSON.stringify(_.get(childRef, 'current.data'))}</div></div>);
};export default App;

子组件

1) forwardRef作用: 封装组件, 直接将ref参数加在props后面(也可以不使用, 自己props定义一下ref需要传参, 父组件一样传ref就行)

2) useImperativeHandle作用和vue3的defineExpose一样, 存储需要暴露给父组件让其获取的数据和函数

import {forwardRef,useEffect,useImperativeHandle,useRef,useState,
} from "react";const RefToGetChild = forwardRef((props:{message:string;}, ref) => {const [data, setData] = useState({});const buttonRef = useRef(null);useEffect(() => {setTimeout(() => {const obj = {a: 1,b: 2,c: 3,d: Array.from({ length: 10 }, (_, i) => ({ id: i })),};setData(obj);}, 1000);}, []);const sayHello = () => {console.log("hello");};const onTest = () => {console.log('test')}useImperativeHandle(ref, () => ({data,buttonRef,onTest,}));return (<div><button ref={buttonRef} onClick={sayHello}>{props.message}</button></div>);
});export default RefToGetChild