数据流

1.reducer通过给第一个参数默认值来设置初始状态
2.view通过store.getState()来获取store里管理的状态
3.view层产生用户操作，调用了actionCreator的方法
4.在actionCreator的方法中，创建标识性的action通过store.dispatch方法传递给reducer'
5.reducer执行，接收到actionCreator传递过来的action来进行判断'
6.reducer经对action的判断后返回了新的状态
7.store里的状态更新后，store.subscribe方法里的函数执行，view重新获取状态

1、创建store.js

import {createStore} from 'redux'
import reducer from './reducer'
const store = createStore(reducer) //Redux 提供createStore这个函数，用来生成 Store。

export default store   

2、创建reducer.js

reducer 纯函数
//第一个参数就是默认的store的state
let _state = {                       //1.reducer通过给第一个参数默认值来设置初始状态'
    todos:[]
}
let count = 0
//注意，reducer必须return出state，这样store才能用到state

const reducer = (state=_state,action)=>{                 
        switch(action.type)         //5.reducer执行，接收到actionCreator传递过来的action来进行判断'
        case 'GET_TODOS':
            state.todos=state.todos.concat(action.todos)
            count = state.todos.length
            console.log(state,111)
            return state;break;
        case 'REMOVE_TODO': //6.reducer经对action的判断后返回了新的状态'
            for(var i =0;i<state.todos.length;i++){
                if(state.todos[i].id==action.id){
                    state.todos.splice(i,1)
                    break;
                }
            }
            return state;break;
        default :
            return state;break;
    }
}
export default reducer

3、actionCreator.js

import axios from 'axios'
import store from './store'
const actionCreator = {
    getTodos(){
        axios.get("./public/json/todos.json").then((res)=>{
            store.dispatch({
                type:'GET_TODOS',
                todos:res.data
            })
        })
    },
    removeTodo(id){           //4.在actionCreator的方法中，创建标识性的action通过store.dispatch方法传递给reducer'
        store.dispatch({
            type:'REMOVE_TODO',
            id
        })
    }
}

export default actionCreator

view层

import React from 'react'

import TodoItem from './TodoItem'

import store from './redux/store'
class TodoBox extends React.Component {
    constructor(props,context){
        super(props,context)
        
        this.state = {
            todos:store.getState().todos     //2.view通过store.getState()来获取store里管理的状态
        }
    }
    
    render(){
        let {todos} = this.state
        return (
            <ul className="list-group todobox">
               {
                       todos.map(function  (todo,i) {
                           return <TodoItem todo={todo} key={todo.id}/>
                       })
               }
            </ul>
        )
    }
    
    componentDidMount(){
        store.subscribe(function  () {     //7.store里的状态更新后，store.subscribe方法里的函数执行，view重新获取状态
            this.setState({todos:store.getState().todos})
        }.bind(this))
    }
}


export default TodoBox


removeTodo(id){         //3.view层产生用户操作，调用了actionCreator的方法
    actions.removeTodo(id)
}