React ToDolist增加功能

补充知识点
1==》npm install prop-types 先安装参数校验包

在B C页面引入
import PropTypes from 'prop-types' //参数限制

    // 验证 参数必要性  B页面
    static propTypes = {
        len: PropTypes.number.isRequired,
        addtod: PropTypes.func.isRequired
    }

// 验证 参数必要性C页面
 static propTypes = { todolist: PropTypes.array.isRequired }

关于todelist的总结

1==》将数据放在父组件中

    constructor(props){
          super(props);
          this.state={
              todolist:[
                  { id: 1, text: "web111" },
                  { id: 2, text: "web222" },
                  { id: 3, text: "web333" }
              ]
          }
    }


2==》将父组件中的数据  传递给子组件(父传子)
 let { todolist}=this.state; //结构
 <C todolist={todolist}></C>


3==》子组件进行渲染
 render() {
        let { todolist } = this.props; 
        console.log("值传递过来",todolist)
        return (
         <ul>
               {todolist.map((item,index)=>{
                 return  <li key={index}>{item.text}</li>
               })}
         </ul>
        )
    }


4==》将父组件的长度  传递给子组件
 <B len={todolist.length} addtod={this.addtod}></B>  父
   



5==》 子组件进行渲染
   render() {
        let { len}=this.props
        return (
            <div>
                <input type="text" ref="conn" /><button onClick={this.add} >123#{len}</button>
            </div>
        )
    }


6==》点击按钮获取到值

    render() {
        let { len}=this.props
        return (
            <div>
                <input type="text" ref="conn" /><button onClick={this.add} >123#{len}</button>
            </div>
        )
    }

    add=()=>{
        console.log(this.refs.conn.value) 

        let uservalu = this.refs.conn.value; //获取值

        let {addtod}=this.props;//父组件想子组件传递了一个方法

        addtod(uservalu)  //调用这个方法

        this.refs.conn.value=""; //清空
    }

7==》父组件给子组件传递方法


8==》子组件调用父组件的方法 并且返回表单中的内容


9==》父组件接受子组件中返回来的数据  更改state

以下是完整代码

A.js 标题

import React, { Component } from "react"
export default class A extends Component {
    render() {
        return (
            <div>我是标题  todo list</div>
        )
    }
}

B.js 表单和按钮

import React, { Component } from "react"
export default class B extends Component {

    add=()=>{
        console.log(this.refs.conn.value) 
        let uservalu = this.refs.conn.value; //获取值

        let {addtod}=this.props;//父组件想子组件传递了一个方法

        addtod(uservalu)  //调用这个方法

        this.refs.conn.value=""; //清空
    }

    render() {
        let { len}=this.props
        return (
            <div>
                <input type="text" ref="conn" /><button onClick={this.add} >123#{len}</button>
            </div>
        )
    }
}

C.js 渲染

import React, { Component } from "react"
export default class C extends Component {
//    constructor(props){
//        super(props);
//        let { todolist}=this.props; 
//    }

    render() {
        let { todolist } = this.props; //它等价于上面的哪一个内容
        console.log("值传递过来",todolist)
        return (
         <ul>
               {todolist.map((item,index)=>{
                 return  <li key={index}>{item.text}</li>
               })}
         </ul>
        )
    }
}

最大父组件DoAddList.js

import React, { Component } from "react"
 
// 引入组件
import A from "./A"
import B from "./B"
import C from "./C"
 
 
export default class DoAddList extends Component {
 
    constructor(props){
          super(props);
          this.state={
              todolist:[
                  { id: 1, text: "web111" },
                  { id: 2, text: "web222" },
                  { id: 3, text: "web333" }
              ]
          }
    }
 
    addtod=(data)=>{
        let con=this.state.todolist;
        con.unshift({ id: this.state.todolist.length + 1, text: data })
 
        // 跟新状态
        this.setState({
            todolist: con
        })
    }
      
    render() {
        let { todolist}=this.state; //结构
        return (
            <div>
              <A></A>
                {/* 将右边的{this.addtod 方法传递给子组件 */}
                <B len={todolist.length} addtod={this.addtod}></B>
                {/*将父组件中的数据  传递给子组件(父传子)*/}
                <C todolist={todolist}></C>
            </div>
        )
    }
}