react 父组件调用子组件中的事件

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()

  }

}

class Child extends Component {

constructor(props){
super(props);
this.state = {value: ''};
}

  componentDidMount(){

    this.props.onRef(this)

  }

  myName = () => {

    this.setState({value:'boonook'});

  }

render(){
return(
<div>
我是子组件
<input value={this.state.value} type="text"/>
</div>
)
}

}