React父组件调用子组件中的方法实例详解

import React, { Component } from 'react';

import Child from './Child';

class Parent extends Component {
  componentDidMount () {
    console.log(this.childRef)
  }
  handleChildEvent = (ref) => {
  	// 将子组件的实例存到 this.childRef 中, 这样整个父组件就能拿到
    this.childRef = ref
  }
  //按钮事件处理
  handleClick = () => {
  	// 通过子组件的实例调用组组件中的方法
    this.childRef.sendMessage()
  }
  render () {
    return (
      <>
        <Child
          onChildEvent={this.handleChildEvent}
        />
        <button onClick={this.handleClick}>Trigger Child Event</button>
      </>
    );
  }
}

export default Parent;

import React, { Component } from 'react';

class Child extends Component {
	//子组件完成挂载时, 将子组件的方法 this 作为参数传到父组件的函数中
  componentDidMount () {
  	// 在子组件中调用父组件的方法,并把当前的实例传进去
    this.props.onChildEvent(this)
  }
  // 子组件的方法, 在父组件中触发
  sendMessage = () => {
    console.log('sending message')
  }
  render () {
    return ( <div>Child</div> );
  }
}

export default Child;

import React, { Component } from 'react';

import ChildCmp from './ChildCmp';

export default class ParentCmp extends Component {
  constructor(props) {
    super(props)
    // 创建Ref
    this.childRef = React.createRef()
  }
  // 按钮事件
  handleClick = () => {
  	// 直接通过 this.childRef.current 拿到子组件实例
    this.childRef.current.sendMessage()
  }
  render () {
    return (
      <>
        <ChildCmp ref={this.childRef} />
        <button onClick={this.handleClick}>Trigger Child Event</button>
      </>
    );
  }
}

import React, { Component } from 'react';

export default class ChildCmp extends Component {
  sendMessage = () => {
    console.log('sending message')
  }
  render () {
    return 'Child';
  }
}

import React, { Component } from 'react';

import ChildCmp from './ChildCmp';

export default class ParentCmp extends Component {
  constructor(props) {
    super(props)
    // 创建 Ref，不通过 React.createRef()
    this.childRef = null
  }
  // 设置 Ref
  setChildRef = (ref) => {
    this.childRef = ref
  }
  // 按钮事件
  handleClick = () => {
    // 直接通过 this.childRef 拿到子组件实例
    this.childRef.sendMessage(`Trigger Child Event from Parent`)
  }

  render () {
    return (
      <>
        <ChildCmp ref={this.setChildRef} />
        <button onClick={this.handleClick}>Trigger Child Event</button>
      </>
    );
  }
}

import { Component } from 'react';

export default class ChildCmp extends Component {
  sendMessage = (message) => {
    console.log('sending message:', message)
  }
  render () {
    return 'Child';
  }
}

import React, { useRef } from 'react';

import Child from './Child';

const Parent = () => {
  // 通过 Hooks 创建 Ref
  const childRef = useRef(null)
  const handleClick = () => {
    childRef.current.sendMessage()
  }
  return (
    <>
      <Child
        ref={childRef}
      />
      <button onClick={handleClick}>Trigger Child Event</button>
    </>
  );
}
export default Parent;

import React, { forwardRef, useImperativeHandle } from 'react';

const Child = forwardRef((props, ref) => {
  //将子组件的方法 暴露给父组件
  useImperativeHandle(ref, () => ({
    sendMessage
  }))
  const sendMessage = () => {
    console.log('sending message')
  }
  return ( <div>Child</div> );
})
export default Child;

 <NavBarX
   item={item}
   current={current}
   getBatchDetails={(id) => this.getBatchDetails(0, id)}
   setId={(id, callback) => this.setState({ id }, callback)}
   onRef={this.onNavBarXRef}
 />

     this.props.setId(prePageId, () => {
        getBatchDetails(prePageId)
      })