React组件传值

（一）父传子

传递：在父组件中子组件的标签上，给子组件绑定一个自定义属性，值为需要传递的数据

接收：在子组件内部通过props进行接收

• 如何限制外部数据的类型

https://react.docschina.org/docs/typechecking-with-proptypes.html

1. 安装prop-types

cnpm install prop-types

2. 引入PorpTypes import ProtoTypes from “prop-types”
3. 配置

组件名称.propTypes = {

​ 属性名称 : PropTypes.类型

}

• 如何定义外部数据的默认值

组件名称.defaultProps = {

​ 属性名称 : 默认值

}

详见下面案例中的one.js

（二）子传父

传递：在子组件内部通过调用this.props.事件函数名称来进行传值

接收：在父组件中子组件的标签上，给子组件绑定一个自定义属性，值为需要传递的数据

（三）非父子

手动封装Observer(事件订阅)

传值的一方调用Observer.$emit ，使用Observer.$on接收

• 组件传值案例

组件传值.png

• index.jsx

import React, { Fragment } from "react";
import One from "./components/one"
import Two from "./components/two"
class App extends React.Component {
    constructor() {
        super();
        this.state = {
            msg: "app组件",
            value: ""
        }
    }
    render() {
        return (
            <div className="app">
                <h2>app组件</h2>
                <h2>接收到子组件的值为:{this.state.value}</h2>
                <One username={this.state.msg} />
                <Two handle={this.handleTwo.bind(this)} />
            </div>
        )
    }
    handleTwo(value) {
        this.setState({
            value
        })
    }
}

export default App;

• one.js

import React, { Component } from "react"
import Three from "./three"
import PropTypes from "prop-types"
class One extends Component {
    render() {
        let { username } = this.props;
        return (
            <div className="One">One组件
                <h2>接受到父组件的值为:{username}</h2>
                <Three />
            </div>
        )
    }
}

One.proTypes = {
    username:ProTypes.string
}
One.defaultProps = {
    username:"默认值"
}

export default One

• two.js

import React, { Component } from "react"
import Observer from "../observer"
class Two extends Component {
    constructor() {
        super();
        this.state = {
            threeVal: ""
        }
        Observer.$on("handle", (value) => {
            this.setState({
                threeVal: value
            })
        })
    }
    render() {
        return (
            <div className="Two">
                Two组件
                <h2>接收到three组件的值为：{this.state.threeVal}</h2>
                <button onClick={this.handleAdd.bind(this)}>点击发送给父组件</button>
            </div>
        )
    }
    handleAdd() {
        this.props.handle('two组件')
    }
}

export default Two

• three.js

import React, { Component } from "react"
import Observer from "../observer"
class Three extends Component {
    render() {
        console.log(1, this)
        return (
            <div className="three">
                three组件
            <button onClick={this.handleSend.bind(this)}>发送到two组件</button>
            </div>
        )
    }
    handleSend() {
        Observer.$emit("handle", "three组件");
    }
}

export default Three

（四）context

Provider-Consumer跨组件传值，相当于vue中的provide/reject

通过context创建一个生产者作为父级，再创建一个消费者组件作为子级使用。

• Consumer必须要有一个函数，返回一个jsx语法

Provider-Consumer.png

• createContext.js

import React, { createContext } from "react";
export let { Provider, Consumer } = createContext();

• index.jsx

import React, { Fragment } from "react";
import One from "./components/one"
import { Provider } from "./createContext"
class App extends React.Component {

    render() {
        return (
            <Provider
                value={{
                    username: "lxc",
                    age: 18
                }}
            >
                <div className="app">
                    app组件
                    <One />
                </div>
            </Provider>
        )
    }
}

export default App;

• two.jsx

import React, { Component } from "react"
import { Consumer } from "../createContext"
class Two extends Component {
    render() {
        return (
            <Consumer>
                {
                    (props) => {
                        return (
                            <div className="Two">
                                two组件
                                <h2>接收app组件传值username:{props.username}                                  </h2>
                            </div>
                        )
                    }
                }
            </Consumer>
        )
    }
}

export default Two