把子元件的引數回傳到父元件中,並且賦值給子元件的一個例項方法.

參考React中文網： http://www.css88.com/react/docs/refs-and-the-dom.html

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()
    }

}

class Child extends Component {    componentDidMount(){        //必須在這裡宣告，所以 ref 回撥可以引用它
        this.props.onRef(this
 
)
    }

    myName = () => alert('我的名字')

    render() {
        return ('lalalala')
    }
}