在react组件的相互调用中，把调用者称为父组件，被调用者称为子组件。父子组件间可以传值：1、父组件向子组件传值时，先将需要传递的值传递给子组件，然后在子组件中，使用props来接收父组件传递过来的值；2、子组件向父组件传值时，需要通过触发方法来传递给父组件。

本教程操作环境：Windows7系统、react18版、Dell G3电脑。

一、React中的组件

react组件就是自己定义的非html标签，规定react组件首字母大写：

class App extends Component{
}

<App />

二、父子组件

组件的相互调用中，把调用者称为父组件，被调用者称为子组件：

import React from 'react';
import Children from './Children';

class Up extends React.Component {
    constructor(props){
        super(props);
        this.state = {
            
        }

    }

    

    render(){
        console.log("render");
        return(
            <div>
                up
                <Children />
            </div>
        )
    }
}

export default Up;

import React from 'react';

class Children extends React.Component{
    constructor(props){
        super(props);
        this.state = {
            
        }
    }
    
    render(){

        return (
            <div>
                Children
            </div>
        )
    }
}

export default Children;

三、父组件给子组件传值

父组件向子组件传值使用props。父组件向子组件传值时，先将需要传递的值传递给子组件，然后在子组件中，使用props来接收父组件传递过来的值。

父组件在调用子组件的时候定义一个属性：

<Children msg="父组件传值给子组件" />

这个值msg会绑定在子组件的props属性上，子组件可以直接使用：

this.props.msg

父组件可以给组件传值，传方法，甚至可以把自己传递给子组件

3.1 传值

import React from 'react';
import Children from './Children';

class Up extends React.Component {
    constructor(props){
        super(props);
        this.state = {
            
        }

    }

    

    render(){
        console.log("render");
        return(
            <div>
                up
                <Children msg="父组件传值给子组件" />
            </div>
        )
    }
}

export default Up;

import React from 'react';

class Children extends React.Component{
    constructor(props){
        super(props);
        this.state = {
            
        }
    }
    
    render(){

        return (
            <div>
                Children
                <br />
                {this.props.msg}
            </div>
        )
    }
}

export default Children;

3.2 传方法

import React from 'react';
import Children from './Children';

class Up extends React.Component {
    constructor(props){
        super(props);
        this.state = {
            
        }

    }

    run = () => {
        console.log("父组件run方法");
    }
    

    render(){
        console.log("render");
        return(
            <div>
                up
                <Children run={this.run} />
            </div>
        )
    }
}

export default Up;

import React from 'react';

class Children extends React.Component{
    constructor(props){
        super(props);
        this.state = {
            
        }
    }

    run = () => {
        this.props.run();
    }
    
    render(){

        return (
            <div>
                Children
                <br />
                <button onClick={this.run}>Run</button>
            </div>
        )
    }
}

export default Children;

3.3 将父组件传给子组件

import React from 'react';
import Children from './Children';

class Up extends React.Component {
    constructor(props){
        super(props);
        this.state = {
            
        }

    }

    run = () => {
        console.log("父组件run方法");
    }
    

    render(){
        console.log("render");
        return(
            <div>
                up
                <Children msg={this}/>
            </div>
        )
    }
}

export default Up;

import React from 'react';

class Children extends React.Component{
    constructor(props){
        super(props);
        this.state = {
            
        }
    }

    run = () => {
        console.log(this.props.msg);
    }
    
    render(){

        return (
            <div>
                Children
                <br />
                <button onClick={this.run}>Run</button>
            </div>
        )
    }
}

export default Children;

四、子组件给父组件传值

子组件向父组件传值通过触发方法来传值

import React from 'react';
import Children from './Children';

class Up extends React.Component {
    constructor(props){
        super(props);
        this.state = {
            
        }

    }

    getChildrenData = (data) => {
        console.log(data);
    }
    

    render(){
        console.log("render");
        return(
            <div>
                up
                <Children upFun={this.getChildrenData}/>
            </div>
        )
    }
}

export default Up;

import React from 'react';

class Children extends React.Component{
    constructor(props){
        super(props);
        this.state = {
            
        }
    }
    
    render(){

        return (
            <div>
                Children
                <br />
                <button onClick={() => {this.props.upFun("子组件数据")}}>Run</button>
            </div>
        )
    }
}

export default Children;

五、父组件中通过refs获取子组件属性和方法

import React from 'react';
import Children from './Children';

class Up extends React.Component {
    constructor(props){
        super(props);
        this.state = {
            
        }

    }

    clickButton = () => {
        console.log(this.refs.children);
    }
    

    render(){
        console.log("render");
        return(
            <div>
                up
                <Children ref="children" msg="test"/>
                <button onClick={this.clickButton}>click</button>
            </div>
        )
    }
}

export default Up;
```
```js
import React from 'react';

class Children extends React.Component{
    constructor(props){
        super(props);
        this.state = {
            title: "子组件"
        }
    }

    runChildren = () => {
        
    }
    
    render(){

        return (
            <div>
                Children
                <br />
            </div>
        )
    }
}

export default Children;
```
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