同步Redux

export default {
    CART_AMOUNT_INCREMENT:‘CART_AMOUNT_INCREMENT‘,
    CART_AMOUNT_DECREMENT:‘CART_AMOUNT_DECREMENT‘,
}

import actionType from ‘./actionType‘
//action有两种写法

//第一种写成一个对象，但不方便传递参数
// return {
//     type:actionType.CART_AMOUNT_INCREMENT
//        payload:{
//            id
//        }
// }

//常用方式
export const increment = (id) => {
    return {
        type:actionType.CART_AMOUNT_INCREMENT,
        payload:{
            id
        }
    }
    
}

export const decrement = (id) => {
    return {
        type:actionType.CART_AMOUNT_DECREMENT,
        payload:{
            id
        }
    }
    
}

//为了避免actionType重复,所以会把actionType放在同一个文件里面同意管理
import actionType from ‘../actions/actionType‘
const initState = [
    {
        id:1,
        title:‘Apple‘,
        price:8888,
        amount:10,
    },
    {
        id:2,
        title:‘华为‘,
        price:999,
        amount:15,
    },
]
//创建reducer, reducer的固定写法是两个参数，第一个就是state并有一个初始值，第二个是action
export default (state = initState,action) => {
    //根据不同的action.type ，做不同的处理，每次返回 一个新的state,返回的类型要一样
    switch(action.type){
        case actionType.CART_AMOUNT_INCREMENT:
            return state.map(
                item =>{
                    if(item.id === action.payload.id){
                        item.amount += 1
                    }
                    return item
                }
            )
            break
            case actionType.CART_AMOUNT_DECREMENT:
                return state.map(
                    item =>{
                        if(item.id === action.payload.id){
                            item.amount -= 1
                        }
                        return item
                    }
                )
                break
        //一定要有default
        default:
            return state
    }
}

import { combineReducers } from ‘redux‘
import cart from ‘./cart‘

export default combineReducers({
    //外部就可以通过store.getState().cart来获取到cartReducer里面的state
    cart
})

//createStore是redux提供的
import { createStore } from ‘redux‘
//引入合并后的reducer
import rootReducer from ‘./reducers‘
//createStore的第一个参数必须是一个reducer，多个reducer在reducers目录下先使用combineReducers合并之后再导出
export default createStore(rootReducer)

import React from ‘react‘
import {render} from ‘react-dom‘
import App from ‘./App‘

import { Provider } from ‘react-redux‘
import store from ‘./store‘
render(
  //用Provider包囊后，所有后代组件都可以使用Redux.connect做链接
  <Provider store={store}>
    <App  />
  </Provider>,
  document.querySelector(‘#root‘)
) 

import React, { Component } from ‘react‘

//connect方法执行后是一个高阶组件
import { connect } from ‘react-redux‘
//导入actionCreators
import { increment,decrement } from ‘../../actions/cart‘

class CartList extends Component {
    
    render() {
        console.log(this.props)
        return (
            <table>
                <thead>
                    <tr>
                        <th>ID</th>
                        <th>商品名称</th>
                        <th>价格</th>
                        <th>操作</th>
                    </tr>
                </thead>
                <tbody>
                    {
                        this.props.cartList.map(item=>{
                            return (
                                <tr key={item.id}>
                                    <td>{item.title}</td>
                                    <td>{item.price}</td>
                                    <td>
                                        <button onClick={this.props.decrement.bind(this,item.id)}>-</button>
                                        <span>{item.amount}</span>
                                        <button onClick={this.props.increment.bind(this,item.id)}>+</button>
                                    </td>
                                    <td></td>
                                </tr>
                            )
                        })
                    }
                    
                </tbody>
            </table>
        )
    }
}
//这里的state实际上就是store.getState()的值
const mapStateToProps = (state) => {
    console.log(state)
    //这里return的值 在组件就可以通过this.props来获取
    return {
        cartList:state.cart
    }
}

// const mapDispatchToProps = dispatch =>{
//     return {
//         add:(id)=> dispatch(increment(id)),
//         decr:(id)=> dispatch(decrement(id)),
//     }
// }

//connect方法有四个参数，常用的就是前面两个
//第一个参数是mapStateToProps,作用就是从store里把state注入到当前组件的props上
//第一个参数是mapDispatchToProps，作用就是把当前组件的方法注入到当前组件的props上
//export default  connect(mapStateToProps,mapDispatchToProps)(CartList)

//第二个参数直接传递对象,这里面是actionCreators,只要传入actionCreators组件内通过
//this.props.actionCreators来调用,会自动注入到dispatch
export default  connect(mapStateToProps, { increment,decrement })(CartList)