21 react-redux

12/16/2021 react

Getting Started with React Redux | React Redux (opens new window)

求和案例 react-redux 基本使用

(1).明确两个概念:
1).UI组件:不能使用任何redux的api,只负责页面的呈现、交互等。
2).容器组件:负责和redux通信,将结果交给UI组件。

(2).如何创建一个容器组件————靠react-redux 的 connect函数
connect(mapStateToProps,mapDispatchToProps)(UI组件)
-mapStateToProps:映射状态,返回值是一个对象
-mapDispatchToProps:映射操作状态的方法,返回值是一个对象

(3).备注1:容器组件中的store是靠props传进去的,而不是在容器组件中直接引入
(4).备注2:mapDispatchToProps,也可以是一个对象

# 完整代码

// 文件结构
\containers
  \Count
    \index.jsx

\redux
    \constant.js
    \count_action.js
    \count_reducer.js
    \store.js

\App.jsx
\index.js
  • 组件定义 Count\index.jsx
import React, { Component } from 'react'
//引入action
import {
	createIncrementAction,
	createDecrementAction,
	createIncrementAsyncAction
} from '../../redux/count_action'
//引入connect用于连接UI组件与redux
import {connect} from 'react-redux'

//定义UI组件
class Count extends Component {

	state = {carName:'奔驰c63'}

	//加法
	increment = ()=>{
		const {value} = this.selectNumber
		this.props.jia(value*1)
	}
	//减法
	decrement = ()=>{
		const {value} = this.selectNumber
		this.props.jian(value*1)
	}
	//奇数再加
	incrementIfOdd = ()=>{
		const {value} = this.selectNumber
		if(this.props.count % 2 !== 0){
			this.props.jia(value*1)
		}
	}
	//异步加
	incrementAsync = ()=>{
		const {value} = this.selectNumber
		this.props.jiaAsync(value*1,500)
	}

	render() {
		//console.log('UI组件接收到的props是',this.props);
		return (
			<div>
				<h1>当前求和为:{this.props.count}</h1>
				<select ref={c => this.selectNumber = 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}>当前求和为奇数再加</button>&nbsp;
				<button onClick={this.incrementAsync}>异步加</button>&nbsp;
			</div>
		)
	}
}

//使用connect()()创建并暴露一个Count的容器组件
export default connect(
	state => ({count:state}),

	//mapDispatchToProps的一般写法
	/* dispatch => ({
		jia:number => dispatch(createIncrementAction(number)),
		jian:number => dispatch(createDecrementAction(number)),
		jiaAsync:(number,time) => dispatch(createIncrementAsyncAction(number,time)),
	}) */

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

constant.js

/* 
	该模块是用于定义action对象中type类型的常量值,目的只有一个:便于管理的同时防止程序员单词写错
*/
export const INCREMENT = 'increment'
export const DECREMENT = 'decrement'

count_action.js

/* 
	该文件专门为Count组件生成action对象
*/
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 createIncrementAction = data => ({type:INCREMENT,data})
export const createDecrementAction = 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 createIncrementAsyncAction = (data,time) => {
	return (dispatch)=>{
		setTimeout(()=>{
			dispatch(createIncrementAction(data))
		},time)
	}
}

count_reducer.js

/* 
	1.该文件是用于创建一个为Count组件服务的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)
*/
import {INCREMENT,DECREMENT} from './constant'

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
	}
}

store.js

/* 
	该文件专门用于暴露一个store对象,整个应用只有一个store对象
*/

//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
export default createStore(countReducer,applyMiddleware(thunk))
  • APP 组件与入口

App.jsx

import React, { Component } from 'react'
import Count from './containers/Count'

export default class App extends Component {
	render() {
		return (
			<div>
				<Count/>
			</div>
		)
	}
}

index.js

import React from 'react'
import ReactDOM from 'react-dom'
import App from './App'
import store from './redux/store'
import {Provider} from 'react-redux'

ReactDOM.render(
	<Provider store={store}>
		<App/>
	</Provider>,
	document.getElementById('root')
)
更新时间: Friday, December 17, 2021 21:19