React(组件间通信--子级向父级传递消息)

子级向父级传递"55"(实质是父级向子级传递了一个方法，供子级调用)

import React, { Component } from 'react';

class Ch extends React.Component{
    constructor(...args){
        super(...args)

        this.num=55
    }
    render(){
        this.props.a(this.num)
        return 

    }
}

class Fa extends React.Component{
    constructor(...args){
        super(...args)
    }
    fn(num){
        alert(num)
    }
    render(){
        return  

        
    }
}
export default Fa;