【React】知识点归纳：使用redux来编写一个简单的应用

Z时代
2024-01-10
分类：综合

react

使用redux来编写一个简单的应用

一、使用redux编写

效果

下载依赖包

源代码

注意

二、使用react编写

效果

源代码

存在问题

一、使用redux编写

效果

下载依赖包

npm install --save redux

源代码

components/app.js

/*
应用组件
 */
import React, {Component} from 'react'
import PropTypes from 'prop-types'
import * as actions from '../redux/actions'
export default class App extends Component {
  static propTypes = {
    store: PropTypes.object.isRequired,
  }
  increment = () => {
    const number = this.refs.numSelect.value * 1
    this.props.store.dispatch(actions.increment(number))
  }
  decrement = () => {
    const number = this.refs.numSelect.value * 1
    this.props.store.dispatch(actions.decrement(number))
  }
  incrementIfOdd = () => {
    const number = this.refs.numSelect.value * 1
    let count = this.props.store.getState()
    if (count % 2 === 1) {
      this.props.store.dispatch(actions.increment(number))
    }
  }
  incrementAsync = () => {
    const number = this.refs.numSelect.value * 1
    setTimeout(() => {
      this.props.store.dispatch(actions.increment(number))
    }, 1000)
  }
  render() {
    return (
      <div>
        <p>
          click {this.props.store.getState()} times {' '}
        </p>
        <select ref="numSelect">
          <option value="1">1</option>
          <option value="2">2</option>
          <option value="3">3</option>
        </select>{' '}
        <button onClick={this.increment}>+</button>
        {' '}
        <button onClick={this.decrement}>-</button>
        {' '}
        <button onClick={this.incrementIfOdd}>increment if odd</button>
        {' '}
        <button onClick={this.incrementAsync}>increment async</button>
      </div>
    )
  }
}

redux/action-types.js

/*
 Action对象的type常量名称模块
 */
export const INCREMENT = 'increment'
export const DECREMENT = 'decrement'

redux/actions.js

/*
action creator模块
 */
import {INCREMENT, DECREMENT} from './action-types'
export const increment = number => ({type: INCREMENT, number})
export const decrement = number => ({type: DECREMENT, number})

redux/reducers.js

/*
根据老的state和指定action, 处理返回一个新的state
 */
import {INCREMENT, DECREMENT} from './action-types'
export function counter(state = 0, action) {
  console.log('counter', state, action)
  switch (action.type) {
    case INCREMENT:
      return state + action.number
    case DECREMENT:
      return state - action.number
    default:
      return state
  }
}

index.js

import React from 'react'
import ReactDOM from 'react-dom'
import {createStore} from 'redux'
import App from './components/app'
import {counter} from './redux/reducers'
// 根据counter函数创建store对象
const store = createStore(counter)
// 定义渲染根组件标签的函数
const render = () => {
  ReactDOM.render(
    <App store={store}/>,
    document.getElementById('root')
  )
}
// 初始化渲染
render()
// 注册(订阅)监听, 一旦状态发生改变, 自动重新渲染
store.subscribe(render)

注意

牢记store的对象功能
getState(): 得到 state
dispatch(action): 分发 action, 触发 reducer 调用, 产生新的 state
subscribe(listener): 注册监听, 当产生了新的 state 时, 自动调用

这里的注册监听subscribe(listener)写在index.js中，一旦状态发生改变, 自动重新渲染。

二、使用react编写

效果

同上

源代码

components/app.js

import React, {Component} from 'react'
export default class App extends Component {
  state = {
    count: 0
  }
  increment = () => {
    const num = this.refs.numSelect.value*1
    const count = this.state.count + num
    this.setState({count})
  }
  decrement = () => {
    const num = this.refs.numSelect.value*1
    const count = this.state.count - num
    this.setState({count})
  }
  incrementIfOdd = () => {
    let count = this.state.count
    if(count%2==1) {
      const num = this.refs.numSelect.value*1
      count += num
      this.setState({count})
    }
  }
  incrementAsync = () => {
    setTimeout(() => {
      const num = this.refs.numSelect.value*1
      const count = this.state.count + num
      this.setState({count})
    }, 1000)
  }
  render () {
    const {count} = this.state
    return (
      <div>
        <p>
          click {count} times {' '}
        </p>
        <select ref="numSelect">
          <option value="1">1</option>
          <option value="2">2</option>
          <option value="3">3</option>
        </select>{' '}
        <button onClick={this.increment}>+</button>{' '}
        <button onClick={this.decrement}>-</button>{' '}
        <button onClick={this.incrementIfOdd}>increment if odd</button>{' '}
        <button onClick={this.incrementAsync}>increment async</button>
      </div>
    )
  }

index.js

import React from 'react'
import ReactDOM from 'react-dom'
import App from './components/app'
ReactDOM.render(<App/>, document.getElementById('root'))