1、目录结构

2、count/index.js

import React, {Component} from "react";
//引入store,用于获取数据
import store from '../../redux/store'
export default class Count extends Component {
    state = {
        count:store.getState()
    }
    componentDidMount() {
        //监测redux中的数据的变化，只要改变，就会调用render
        store.subscribe(()=>{
            this.setState({
                count:store.getState()
            })
        })
    }

    //加法
    increment=()=>{
        const {value} = this.selectNum
        //通知redux 改变
        store.dispatch({type:'increment',data:parseInt(value)})
     }
     //减法
    decrement=()=>{
        const {value} = this.selectNum
        store.dispatch({type:'decrement',data:parseInt(value)})
     }
     //奇数加
    incrementIfOdd=()=>{
        const {value} = this.selectNum
        const {count} = this.state
        if(count%2!==0)
        {
            store.dispatch({type:'increment',data:parseInt(value)})
        }
     }
     //异步加
    incrementAsync=()=>{
        const {value} = this.selectNum
        const {count} = this.state
        setTimeout(()=>{
            store.dispatch({type:'increment',data:parseInt(value)})
        },500)
     }
    render()
    {
        return(
            <div>
               <h1>当前求和为：{store.getState()}</h1>
                <select ref={(c)=>this.selectNum=c}>
                    <option value="1">1</option>
                    <option value="2">2</option>
                    <option value='3'>3</option>
                </select>&nbsp;
                <button onClick={this.increment}>+</button>&nbsp;
                <button onClick={this.decrement}>-</button>&nbsp;
                <button onClick={this.incrementIfOdd}>当前求和为奇数在加</button>&nbsp;
                <button onClick={this.incrementAsync}>异步加</button>&nbsp;
            </div>
        );
    }

}

3、redux/count_reducer.js

/*
    1.该文件是用于创建一个为count服务的reducer，reducer的本质就是一个函数
    2.reducer函数会接到两个参数，分别为：之前的状态(preState)，动作对象(action)

*/
const initState = 0
export default function countReducer(preState=initState,action) {
    console.log('countReducer',preState,action)
    const {type,data} = action
    // 根据type决定如何加工数据
    switch (type){
        case 'increment':
            console.log('@')
            return preState + data
        case 'decrement':
            return preState - data
        default:
            return preState
    }
}

/redux/store.js

/*
    该文件专门用于创建一个为Count组件服务的store对象
 */
//引入createStore,专门创建redux中最为核心的store对象
import {createStore} from 'redux'
//引入cunter.redux.js文件
import countReducer from './count_reducer'
//暴露store
export default createStore(countReducer)

4、src/app.js

import React, {Component} from "react";
import Count from "./components/Count";
export default class App extends Component {
    render()
    {
        return(
            <div>
                <Count></Count>
            </div>
        );
    }
}

5、src/index.js

import React from "react";
import ReactDOM from 'react-dom'
import App from './App'
ReactDOM.render(<App/>,document.getElementById('root'))