React-redux应用

Snipaste_20200519_142105.jpg

老样子，依旧从最简单的计数器开始学习。。。。

推荐直接用react脚手架进行操作

这是一个最简单的react-redux实现

          
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          import React, { Component } from 'react'
import PropTypes from 'prop-types'
import ReactDOM from 'react-dom'
import { createStore } from 'redux'
import { Provider, connect } from 'react-redux'

// React component
class Counter extends Component {
  render() {
    const { value, onIncreaseClick } = this.props
    return (
      <div>
        <span>{value}</span>
        <button onClick={onIncreaseClick}>Increase</button>
      </div>
    )
  }
}

Counter.propTypes = {
  value: PropTypes.number.isRequired,
  onIncreaseClick: PropTypes.func.isRequired
}

// Action
const increaseAction = { type: 'increase' }

// Reducer
function counter(state = { count: 0 }, action) {
  const count = state.count
  switch (action.type) {
    case 'increase':
      return { count: count + 1 }
    default:
      return state
  }
}

// Store
const store = createStore(counter)

// Map Redux state to component props
function mapStateToProps(state) {
  return {
    value: state.count
  }
}

// Map Redux actions to component props
function mapDispatchToProps(dispatch) {
  return {
    onIncreaseClick: () => dispatch(increaseAction)
  }
}

// Connected Component
const App = connect(
  mapStateToProps,
  mapDispatchToProps
)(Counter)

ReactDOM.render(
  <Provider store={store}>
    <App />
  </Provider>,
  document.getElementById('root')
)

介绍一下各部分功能

Store

const store = createStore(reducer)

创建一个综合状态管理的仓库

Reducer

通常在这里分发要进行的操作，根据当前state和指定action返回一个新的state，管理状态数据

action

这是包含n个用来创建action的工厂函数(action creator) 在这里写改变状态的函数

接下来我们把他们分成模块管理，再来写一个demo

推荐写法：

Snipaste_20200519_154631.jpg

store.js

redux最核心的管理对象: store

          
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          import {createStore} from 'redux'

import reducer from './reducer'

export default createStore(reducer) // 创建store对象内部会第一次调用reducer()得到初始状态值

action-types.js 用来写常量

          
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          //包含n个action type常量名称的模块
export const INCREMENT = 'increment'
export const DECREMENT = 'decrement'

action.js

          
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          //包含n个用来创建action的工厂函数(action creator)

import {INCREMENT, DECREMENT} from './action-types'

//增加的action
export const increment = number => ({type: INCREMENT, data: number})

//减少的action
export const decrement = number => ({type: DECREMENT, data: number})

reducer.js

          
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          import {INCREMENT, DECREMENT} from './action-types'

//管理count状态数据的reducer

export default function count(state=1, action) {
  console.log('count()', state, action)
  switch (action.type) {
    case INCREMENT:
      return state + action.data
    case DECREMENT:
      return state - action.data
    default:
      return state
  }
}

index.js 入口文件

          
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          //入口文件
import React from 'react'
import ReactDOM from 'react-dom'
import { Provider } from 'react-redux'

import App from './App'
import store from './redux/store'

ReactDOM.render((
  <Provider store={store}>
    <App />
  </Provider>),
  document.getElementById('root')
)

App.js count组件

          
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          import React, { Component } from 'react'
import { increment, decrement } from './redux/actions'
import { connect } from 'react-redux'


class Counter extends Component {
  increment = () => {
    this.props.increment(1)
  }
  decrement = () => {
    this.props.decrement(1)
  }
  render() {
    const count = this.props.count

    return (
      <div>
        <p>count: {count} </p>
        <button onClick={this.increment}>+</button>&nbsp;&nbsp;
        <button onClick={this.decrement}>-</button>&nbsp;&nbsp;
      </div>
    )
  }
}

// 指定向Counter传入哪些一般属性(属性值的来源就是store中的state)
const mapStateToProps = (state) => ({ count: state })
// 指定向Counter传入哪些函数属性
/*如果是函数, 会自动调用得到对象, 将对象中的方法作为函数属性传入UI组件*/
/*const mapDispatchToProps = (dispatch) => ({
  increment: (number) => dispatch(increment(number)),
  decrement: (number) => dispatch(decrement(number)),
})*/
/*如果是对象, 将对象中的方法包装成一个新函数, 并传入UI组件 */
const mapDispatchToProps = { increment, decrement }

export default connect(
  mapStateToProps,
  mapDispatchToProps
)(Counter)

接下来我们需要实现异步的，再来写一个demo，多用于网络请求

这里我们要用到的中间件

'redux-thunk'的thunk，

redux的applyMiddleware，

开发工具(可选,用于redux-devtools的调试) 'redux-devtools-extension'的composeWithDevTools

store.js

          
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import {createStore, applyMiddleware} from 'redux'
import thunk from 'redux-thunk' // 用来实现redux异步的redux中间件插件
import {composeWithDevTools} from 'redux-devtools-extension'
import reducer from './reducer'

export default createStore(reducer, composeWithDevTools(applyMiddleware(thunk))) 
//生产可以把composeWithDevTools()包装去除

action-types.js 用来写常量

          
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          //包含n个action type常量名称的模块
export const INCREMENT = 'increment'
export const DECREMENT = 'decrement'

action.js 这里我们用定时器添加一个异步的操作

          
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          //包含n个用来创建action的工厂函数(action creator)

import {INCREMENT, DECREMENT} from './action-types'

//增加的action
export const increment = number => ({type: INCREMENT, data: number})

//减少的action
export const decrement = number => ({type: DECREMENT, data: number})


//增加的异步action: 返回的是函数

export const incrementAsync = number => {
  return dispatch => {
    // 1. 执行异步(定时器, ajax请求, promise)
    setTimeout(() => {
      // 2. 当前异步任务执行完成时, 分发一个同步action
      dispatch(increment(number))
    }, 1000)
  }
}

reducer.js

这里我们添加一个redux的combineReducers接收包含所有reducer函数的对象, 返回一个新的reducer函数(总reducer) 总的reducer函数管理的state的结构

          
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          import {INCREMENT, DECREMENT} from './action-types'

//管理count状态数据的reducer

function count(state=1, action) {
  console.log('count()', state, action)
  switch (action.type) {
    case INCREMENT:
      return state + action.data
    case DECREMENT:
      return state - action.data
    default:
      return state
  }
}


function user(state = {admin:"admin"}, action) {
  switch (action.type) {
    default:
      return state
  }
}

export default combineReducers({
  count,
  user
})

index.js 入口文件

          
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          //入口文件
import React from 'react'
import ReactDOM from 'react-dom'
import { Provider } from 'react-redux'

import App from './App'
import store from './redux/store'

ReactDOM.render((
  <Provider store={store}>
    <App />
  </Provider>),
  document.getElementById('root')
)

App.js count组件

          
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          import React, { Component } from 'react'
import { increment, decrement,incrementAsync} from './redux/actions'
import { connect } from 'react-redux'


class Counter extends Component {

  increment = () => {
    this.props.increment(1)
  }
  decrement = () => {
    this.props.decrement(1)
  }
  
  incrementAsync = () => {
    this.props.incrementAsync(2)
  }
  render() {
    const count = this.props.count
    const user = this.props.user
    console.log(user)
    return (
      <div>
        <p>user: {user.name} </p>
        <p>count: {count} </p>
        <button onClick={this.increment}>+</button>&nbsp;&nbsp;
        <button onClick={this.decrement}>-</button>&nbsp;&nbsp;
        <button onClick={this.incrementAsync}>异步+2</button>&nbsp;&nbsp;
      </div>
    )
  }
}

//注意此处写法
const mapStateToProps = (state) => ({ count: state.count ,user: state.user })
const mapDispatchToProps = { increment, decrement,incrementAsync}

export default connect(
  mapStateToProps,
  mapDispatchToProps
)(Counter)
———end———
（完）
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