// 父組件
import React, {Component} from 'react';
export default class Parent extends Component {
    render() {
        return(
            <div>
                <Child onRef={this.onRef} />
                <button onClick={this.click} >click</button>
            </div>
        )
    }
    onRef = (ref) => {
        this.child = ref
    }
    click = (e) => {
        this.child.myName()
    }
}

//子組件
class Child extends Component {    
   componentDidMount(){        //必須在這里聲明，所以 ref 回調可以引用它
        this.props.onRef(this)
    }
    myName = () => alert('my name is haorooms blogs')
    render() {
        return (<div>haorooms blog test</div>)
    }
}

/* FComp 父組件 */
import {useRef} from 'react';
import ChildComp   from './child'
const FComp = () => {
    const childRef = useRef();
    const updateChildState = () => {
        // changeVal就是子組件暴露給父組件的方法
        childRef.current.changeVal(99);
    }
    return (
        <>
            <ChildComp ref={childRef} />
            <button onClick={updateChildState}>觸發子組件方法</button>
        </>
    )
}

import React, { useImperativeHandle, forwardRef } from "react"
let Child = (props, ref) => {
 const [val, setVal] = useState();
  useImperativeHandle(ref, () => ({ // 暴露給父組件的方法
     getInfo,
      changeVal: (newVal) => {
          setVal(newVal);
        },
      refreshInfo: () => {
        console.log("子組件refreshInfo方法")
    }
  }))

  const getInfo = () => {
    console.log("子組件getInfo方法")
  }

  return (
    <div>子組件</div>
  )
}
Child = forwardRef(Child)
export default Child

// 父組件class
class Parent extends Component{
  child= {} //主要加這個
  handlePage = (num) => {
    // this.child.
    console.log(this.child.onChild())
  }
   onRef = ref => {
    this.child = ref
  }
render() {
   return {
     <ListForm onRef={this.onRef} />
   }
 }
}

// 子組件hooks
import React, { useImperativeHandle } from 'react'
const ListForm = props => {
  const [form] = Form.useForm()

  //重置方法
  const onReset = () => {
    form.resetFields()
  }
}

 useImperativeHandle(props.onRef, () => ({
    // onChild 就是暴露給父組件的方法
    onChild: () => {
      return form.getFieldsValue()
    }
  }))
  ..............

//父組件hooks
 let richTextRef = {};
// richTextRef.reseditorState();調用子組件方法
  <RichText 
      getRichText={getRichText} 
      content={content} 
      onRef={ref => richTextRef = ref} 
  />

//子組件class
  componentDidMount = () => {
    this.props.onRef && this.props.onRef(this);// 關鍵部分
  }

   reseditorState = (content) => {
    this.setState({
      editorState: content ||'-',
    })
  }