├─component
│   connect.js
│   counter.js
│
└─store
    index.js

import React from "react";
import ReactDom,{render} from "react-dom";
import Couter from "./component/counter";
import {Provider} from "./component/connect" import store from "./store/index"  ReactDom.render(<Provider store={store}><Couter/></Provider>,document.getElementById("root"));

import {createStore} from "redux";
function reducer(state={number:0},action) {
  switch (action.type){
    case "add":
      return {number:state.number+action.count}
    default:
      return state;
  }
}

export default createStore(reducer);

import React from "react";
import PropTypes from "prop-types";
//Provider是一个组件 接受一个store属性 将其内容挂载在上下文context //这样后代才可以都有办法拿到 class Provider extends React.Component{

  static childContextTypes={
    //设置上下文的类型是对象
 store:PropTypes.object
 }

  getChildContext(){
    //获取并设置后代上下文的内容
 return {store:this.props.store}
  }
  render(){
    return this.props.children
 }
}

let connect=(mapStateToProps,mapDispatchToProps)=>(comp)=>{
  return class Proxy extends React.Component{
    static contextTypes={
      store:PropTypes.object
 }
    constructor(props,context){
      super(props);
      //将参数mapStateToProps 的解构赋值 代理组件的状态
 this.setState=mapStateToProps(context.store.getState())
    }
    componentDidMount(){
      this.context.store.subscribe(()=>{
        this.setState(mapStateToProps(this.context.store.getState()))
      })
    }
    render(){
      return <comp {...this.state} {...mapDispatchToProps(this.context.store.dispatch)}/>
    }
  }
}

export {Provider,connect}

import React from "react";
import {connect} from "./connect";
export default class Counter extends React.Component{
  constructor(props){
    super(props);
  }

  render(){
    return (
      <div>
        <button onClick={()=>{
          this.props.add(5);
        }}>+</button>
        {this.props.n}
      </div>
    )
  }
}

let mapStateToProps=(state)=>{
  return {n:state.number}
};
let mapDispatchToProps=(dispatch)=>{
  return {
    add:(count)=>{
      dispatch({type:"add",count:count})
    }
  }
}

export default connect(mapStateToProps,mapDispatchToProps)(Counter)