redux工作原理讲解及使用方法

store.dispatch(action);

let nextState = todoApp(previousState, action);

// 设置监听函数
store.subscribe(listener);

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

//引入createStore，专门用于创建redux中最为核心的store对象
import {createStore，applyMiddleware} from 'redux'
//引入为Count组件服务的reducer
import countReducer from './count_reducer'
//引入redux-thunk，用于支持异步action
import thunk from 'redux-thunk'
//暴露store  
//applyMiddleware 是中间位 中使用thunk
export default createStore(countReducer,applyMiddleware(thunk))

const initState = 0 //初始化状态
export default function countReducer(preState=initState,action){
	// console.log(preState);
	//从action对象中获取：type、data
	const {type,data} = action
	//根据type决定如何加工数据
	switch (type) {
		case 'increment': //如果是加
			return preState + data
		case 'decrement': //若果是减
			return preState - data
		default:
			return preState
	}
}

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

//subscribe当store中数据发生变化就会更新数据,写在这里是让全局拥有
store.subscribe(()=>{
	ReactDOM.render(<App/>,document.getElementById('root'))
})

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

//引入connect用于连接UI组件与redux
import {connect} from 'react-redux'

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function mapStateToProps(state){
	return {count:state}
}
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function mapDispatchToProps(dispatch){
	return {
		jia:number => dispatch(createIncrementAction(number)),
		jian:number => dispatch(createDecrementAction(number)),
		jiaAsync:(number,time) => dispatch(createIncrementAsyncAction(number,time)),
	}
}
//使用connect()()创建并暴露一个Count的容器组件
export default connect(mapStateToProps,mapDispatchToProps)(CountUI)
//改良
export default connect(
	state => ({count:state}),
	
	//mapDispatchToProps的一般写法
	

	//mapDispatchToProps的简写
	{
		jia:createIncrementAction,
		jian:createDecrementAction,
		jiaAsync:createIncrementAsyncAction,
	}
)(Count)

import {INCREMENT,DECREMENT} from '../constant'

//同步action，就是指action的值为Object类型的一般对象
export const increment = data => ({type:INCREMENT,data})
export const decrement = data => ({type:DECREMENT,data})

//异步action，就是指action的值为函数,异步action中一般都会调用同步action，异步action不是必须要用的。
export const incrementAsync = (data,time) => {
	return (dispatch)=>{
		setTimeout(()=>{
			dispatch(increment(data))
		},time)
	}
}