Redux使用详解

前言

本文对redux相关使用的总结，利用一个简单的计数器应用介绍来flux、redux、react-redux、redux-actions等相关类库的使用。

初始代码以下是该示例的初始代码，一个不使用redux的普通计数器应用。

import React from 'react'class Calculate extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
      count: 0
    }
  }
  increase = () => {
    this.setState({
      count: this.state.count + 1
    })
  }
  decrease = () => {
    this.setState({
      count: this.state.count - 1
    })
  }
  render() {
    return(
      <div>
        <h1>{this.state.count}</h1>
        <div>
          <button type="button" onClick={this.increase}>Increase</button>
          <button type="button" onClick={this.decrease}>Decrease</button>
        </div>
      </div>
    )
  }}export default Calculate

Flux

React是单向数据流，组件状态的维护是靠父子组件之间逐层传递来实现的，当应用层级较深时，这种方式就会显得比较繁琐。对此，社区提出了不少解决的方案，目前的最佳实践是Redux。

Redux严格意义上来讲是Flux的一种简洁的实现，在介绍Redux之前，我们先使用flux来重构这个计数器应用。

Flux主要流程有4部分，action、dispatcher、store、view，在该示例中我们需要使用到flux和events两个npm包来实现。

首先，在基础模板上建立目录如下

actionType.js用来定义常量，然后导出,该示例有加和减两种action。

export const INCREASE = 'INCREASE'export const DECREASE = 'DECREASE'
dispatcher.js用来定义dispatcher并导出
import { Dispatcher } from 'flux'class CalculateDispatcherClass extends Dispatcher {
handleAction(action) {
this.dispatch({
type: action.type,
payload: action.payload    })
}}const CalculateDispatcher = new CalculateDispatcherClass()export default CalculateDispatcher
action.js使用导入的action类别以及上面定义的dispatcher来定义action。
import {
INCREASE,
DECREASE} from '../constants/actionTypes'import CalculateDispatcher from '../dispatcher/dispatcher'const action = {
increase(value = 1) {
CalculateDispatcher.handleAction({
type: INCREASE,
payload: value    })
},
decrease(value = 1) {
CalculateDispatcher.handleAction({
type: DECREASE,
payload: value    })
}} export default action

最后在store.js中整合

import CalculateDispatcher from '../dispatcher/dispatcher'import { EventEmitter } from 'events'import {
  INCREASE,
  DECREASE} from '../constants/actionTypes'const store = {
  count: 0}class CalculateStoreClass extends EventEmitter {
  addIncreaseListener(callBack) {
    this.on(INCREASE, callBack)
  }
addDecreaseListener(callBack) {
this.on(DECREASE, callBack)
}
getStore() {
return store  }}const CalculateStore = new CalculateStoreClass()CalculateDispatcher.register((action) => {
switch(action.type) {
case INCREASE:
store.count += action.payload
CalculateStore.emit(INCREASE)
break
case DECREASE:
store.count -= action.payload
CalculateStore.emit(DECREASE)
break
default:
return true
}
return true})export default CalculateStore

最后calculate.js存放我们的视图组件

import React from 'react'import Store from '../store/store'import Action from '../action/action'class Calculate extends React.Component {
  constructor(props) {
    super(props)
    this.state = {
      count: 0
    }
  }
  componentDidMount() {
    Store.addDecreaseListener(this.updateState)
    Store.addIncreaseListener(this.updateState)
  }
  updateState = () => {
    this.setState({
      count: Store.getStore().count    })
  }
  increase = () => {
    Action.increase()
  }
  decrease = () => {
    Action.decrease()
  }
  render() {
    return(
      <div>
        <h1>{this.state.count}</h1>
        <div>
          <button type="button" onClick={this.increase}>Increase</button>
          <button type="button" onClick={this.decrease}>Decrease</button>
        </div>
      </div>
    )
  }}export default Calculate

Redux

了解来Flux之后，就可以使用Redux了，Redux和Flux的不同在与将dispatcher换成了reducer

首先看一下项目结构，与flux的基本没有区别，只是将dispatcher换成了reducer

该示例中不仅使用了redux, 还使用了react-redux,使得redux和react项目更容易结合，使用了redux-actions,使action和reducer中类型的判断更加简单。

actionType.js

export const INCREASE = 'INCREASE'export const DECREASE = 'DECREASE'
action.js 利用redux-actions来创建action
import { INCREASE, DECREASE} from '../constants/actionTypes'import { createActions} from 'redux-actions'const Action = createActions({
[INCREASE]: (value = 1) => ({
payload: value  }),
[DECREASE]: (value = 1) => ({
payload: value  })})export default Action

reducer.js 同样，利用redux-actions来处理reducer

import { INCREASE, DECREASE } from '../constants/actionTypes'import { handleActions} from 'redux-actions'const reducer = handleActions({
  [INCREASE]: (state, action) => (Object.assign({}, state, { count: state.count + action.payload.payload})),
  [DECREASE]: (state, action) => (Object.assign({}, state, { count: state.count - action.payload.payload}))}, {
  count: 0})export  default reducer

store.js 利用redux创建store

import { createStore } from 'redux'import reducer from '../reducer/reducer'const store = createStore(reducer)export default store

calculate.js 利用react-redux来连接react和redux

import React from 'react'import Action from '../action/action'import { connect } from 'react-redux'class Calculate extends React.Component {
  increase = () => {
    this.props.increase()
  }
  decrease = () => {
    this.props.decrease()
  }
  render() {
    return(
      <div>
        <h1>{this.props.count}</h1>
        <div>
          <button type="button" onClick={this.increase}>Increase</button>
          <button type="button" onClick={this.decrease}>Decrease</button>
        </div>
      </div>
    )
  }}const mapStateToProps = (state) => {
  return {
    count: state.count  }}export default connect(mapStateToProps, Action)(Calculate)

最后，在App.js中使用Provider将store传入

import React from 'react'import Calculate from './component/calculate'import { Provider } from 'react-redux'import store from './store/store'class App extends React.Component {
  render() {
    return (
      <Provider store={store}>
        <Calculate />
      </Provider>
    )
  }}export default App

本文使用 mdnice 排版