store.dispatch(action);

let nextState = todoApp(previousState, action);

// 設(shè)置監(jiān)聽函數(shù)
store.subscribe(listener);

function listerner() {
  let newState = store.getState();
  component.setState(newState);   
}

//引入createStore，專門用于創(chuàng)建redux中最為核心的store對(duì)象
import {createStore，applyMiddleware} from 'redux'
//引入為Count組件服務(wù)的reducer
import countReducer from './count_reducer'
//引入redux-thunk，用于支持異步action
import thunk from 'redux-thunk'
//暴露store  
//applyMiddleware 是中間位 中使用thunk
export default createStore(countReducer,applyMiddleware(thunk))

const initState = 0 //初始化狀態(tài)
export default function countReducer(preState=initState,action){
	// console.log(preState);
	//從action對(duì)象中獲取：type、data
	const {type,data} = action
	//根據(jù)type決定如何加工數(shù)據(jù)
	switch (type) {
		case 'increment': //如果是加
			return preState + data
		case 'decrement': //若果是減
			return preState - data
		default:
			return preState
	}
}

// 公共 index.js
import store from './redux/store'

//subscribe當(dāng)store中數(shù)據(jù)發(fā)生變化就會(huì)更新數(shù)據(jù),寫在這里是讓全局擁有
store.subscribe(()=>{
	ReactDOM.render(<App/>,document.getElementById('root'))
})

//引入Count的UI組件
import CountUI from '../../components/Count'

//引入connect用于連接UI組件與redux
import {connect} from 'react-redux'

-------------------------------------------------------------
/* 
	1.mapStateToProps函數(shù)返回的是一個(gè)對(duì)象；
	2.返回的對(duì)象中的key就作為傳遞給UI組件props的key,value就作為傳遞給UI組件props的value
	3.mapStateToProps用于傳遞狀態(tài)
*/
function mapStateToProps(state){
	return {count:state}
}
-----------------------------------------------------------------
/* 
	1.mapDispatchToProps函數(shù)返回的是一個(gè)對(duì)象；
	2.返回的對(duì)象中的key就作為傳遞給UI組件props的key,value就作為傳遞給UI組件props的value
	3.mapDispatchToProps用于傳遞操作狀態(tài)的方法
*/
function mapDispatchToProps(dispatch){
	return {
		jia:number => dispatch(createIncrementAction(number)),
		jian:number => dispatch(createDecrementAction(number)),
		jiaAsync:(number,time) => dispatch(createIncrementAsyncAction(number,time)),
	}
}
//使用connect()()創(chuàng)建并暴露一個(gè)Count的容器組件
export default connect(mapStateToProps,mapDispatchToProps)(CountUI)
//改良
export default connect(
	state => ({count:state}),
	
	//mapDispatchToProps的一般寫法
	/* dispatch => ({
		jia:number => dispatch(createIncrementAction(number)),
		jian:number => dispatch(createDecrementAction(number)),
		jiaAsync:(number,time) => dispatch(createIncrementAsyncAction(number,time)),
	}) */

	//mapDispatchToProps的簡(jiǎn)寫
	{
		jia:createIncrementAction,
		jian:createDecrementAction,
		jiaAsync:createIncrementAsyncAction,
	}
)(Count)

/* 
	該文件專門為Count組件生成action對(duì)象
*/
import {INCREMENT,DECREMENT} from '../constant'

//同步action，就是指action的值為Object類型的一般對(duì)象
export const increment = data => ({type:INCREMENT,data})
export const decrement = data => ({type:DECREMENT,data})

//異步action，就是指action的值為函數(shù),異步action中一般都會(huì)調(diào)用同步action，異步action不是必須要用的。
export const incrementAsync = (data,time) => {
	return (dispatch)=>{
		setTimeout(()=>{
			dispatch(increment(data))
		},time)
	}
}