React 子组件给父组件传值、整个组件、方法

一、准备工作

1.定义一个父组件，名字为Parent

/src/component/Parent.js

import React, {Component} from 'react'

export default class Parent extends Component {
    constructor(props) {
        super(props)
        this.state = {
            name: '我是父组件',
            msg: '父组件传值给子组件'
        }
    }

    render() {
        return (
            <div>
                <h2>{ this.state.name }</h2>
            </div>
        )
    }
}

2.定义一个子组件 ，名字为Children

/src/component/Children.js

import React, {Component} from 'react'

export default class Children extends Component {
    constructor(props) {
        super(props)
        this.state = {
            name: '我是子组件',
            msg: '子组件传值给父组件'
        }
    }

    render() {
        return (
            <div>
                <h2>{ this.state.name }</h2>
            </div>
        )
    }
}

3.先在App.js里引入父组件Parent

/src/App.js

import React from 'react';
import Parent from './component/Parent'

function App() {
  return (
      <div>
          <Parent/>
      </div>
  );
}

export default App;

运行项目：

编译成功 界面如图所示，http://localhost:3000/

4.父组件Parent引入子组件Children

import React, {Component} from 'react'
import Children from './Children'

export default class Parent extends Component {
    constructor(props) {
        super(props)
        this.state = {
            name: '我是父组件',
            msg: '父组件传值给子组件'
        }
    }

    render() {
        return (
            <div>
                <h2>{ this.state.name }</h2>
                <h3>我要引入子组件了：</h3>
                <hr/>
                <Children/>
            </div>
        )
    }
}

已成功引入子组件

二、子组件Children传值(msg)给父组件Parent

子组件传值给父组件的步骤：

1. 父组件在调用子组件时，传入一整个组件给子组件<Children parent={ this } />
2. 父组件中定义一个方法getChildrenMsg(resulet, msg)，用来获取子组件传来的值以及执行其他操作
3. 子组件在通过this.props来获取到一整个组件this.props.parent或者this.props[parent]
4. 子组件调用父组件步骤2里定义的方法，通过bind绑定传值

Parent:

import React, {Component} from 'react'
import Children from './Children'

export default class Parent extends Component {
    constructor(props) {
        super(props)
        this.state = {
            name: '我是父组件',
            msg: '父组件传值给子组件',
            childrenMsg: ''
        }
    }

    getChildrenMsg = (result, msg) => {
        // console.log(result, msg)
        // 很奇怪这里的result就是子组件那bind的第一个参数this，msg是第二个参数
        this.setState({
            childrenMsg: msg
        })
    }

    render() {
        return (
            <div>
                <h2>{ this.state.name }</h2>
                <h3>子组件传来的值为：{ this.state.childrenMsg }</h3>
                <h3>我要引入子组件了：</h3>
                <hr/>
                <Children parent={ this } />
            </div>
        )
    }
}

Children:

import React, {Component} from 'react'

export default class Children extends Component {
    constructor(props) {
        super(props)
        this.state = {
            name: '我是子组件',
            msg: '子组件传值给父组件'
        }
    }

    toParent = () => {
        // console.log(this.props.parent.getChildrenMsg.bind(this, this.state.msg))
        this.props.parent.getChildrenMsg(this, this.state.msg)
    }

    render() {
        return (
            <div>
                <h2>{ this.state.name }</h2>
                <button onClick={ this.toParent }>子组件传入给父组件</button>
            </div>
        )
    }
}

三、子组件Children给父组件Parent传一整个组件（父组件获取整个子组件）

子组件给父组件传一整个组件（父组件获取整个子组件）的步骤：

1. 父组件在调用子组件时，通过ref属性，拿到整个子组件<Children ref='children'>
2. 父组件中通过this.refs.children或者this.refs[children]获取到一整个子组件实例（注意，要在DOM加载后才能获取）

Parent:

import React, {Component} from 'react'
import Children from './Children'

export default class Parent extends Component {
    constructor(props) {
        super(props)
        this.state = {
            name: '我是父组件',
            msg: '父组件传值给子组件',
            childrenMsg: ''
        }
    }

    getChildrenMsg = () => {
        this.setState({
            childrenMsg: this.refs['children'].state.msg
        })
    }

    render() {
        return (
            <div>
                <h2>{ this.state.name }</h2>
                <button onClick={ this.getChildrenMsg }>获取更新子组件的msg值</button>
                <h3>子组件传来的值为：{ this.state.childrenMsg }</h3>
                <h3>我要引入子组件了：</h3>
                <hr/>
                <Children ref="children" />
            </div>
        )
    }
}

Children:

import React, {Component} from 'react'

export default class Children extends Component {
    constructor(props) {
        super(props)
        this.state = {
            name: '我是子组件',
            msg: '子组件传值给父组件'
        }
    }

    render() {
        return (
            <div>
                <h2>{ this.state.name }</h2>
                <h3>子组件的msg为：{ this.state.msg }</h3>
            </div>
        )
    }
}

初始页面，点击按钮
点击按钮后

四、子组件Children给父组件Parent传方法

在第三点获取到整个组件的前提上，再获取方法，所以不详细讲了。