Redux基本使用
纯函数:1.函数内部不能依赖函数外部变量;2.不能产生副作用,在函数内部改变函数外部的变量
React只帮我们解决了DOM的渲染过程,State还是要由我们自己来管理------redux可帮助我们进行管理
Redux三大特点
1.单一数据源:整个应用的状态存储在一个单一的对象树,且该对象树只存储在一个store中
2.State是只读的:状态是不可直接修改的,必须通过触发一个"action"来发起状态的变更
3.使用纯函数来完成状态变更 :通过reducer 将旧state 和actions 联系在一起,并返回一个新的state;不产生任何副作用。
Redux测试项目搭建
step1:项目初始化
npm init
step2:安装redux
npm i redux
step3:创建store仓库,并存储数据
javascript
const { createStore } = require('redux');
const {reducer} = require('./reducer');
// 创建的store
const store = createStore(reducer);
module.exports = store;
step4:创建reducer函数
javascript
const { ADD_NUMBER, CHANGE_NAME } = require("./constants")
// 初始化的数据
const initialState = {
name: "why",
counter: 100
}
function reducer(state = initialState, action) {
switch(action.type) {
case CHANGE_NAME:
return { ...state, name: action.name }
case ADD_NUMBER:
return { ...state, counter: state.counter + action.num }
default:
return state
}
}
module.exports = reducer
注意:在该代码中,我们将action的类型封装到了constants.js文件中,方便复用
javascript
const ADD_NUMBER = "add_number"
const CHANGE_NAME = "change_name"
module.exports = {
ADD_NUMBER,
CHANGE_NAME
}
step5:通过action来修改state
将它封装到一个单独的文件中
javascript
const { ADD_NUMBER, CHANGE_NAME } = require("./constants")
const changeNameAction = (name) => ({
type: CHANGE_NAME,
name
})
const addNumberAction = (num) => ({
type: ADD_NUMBER,
num
})
module.exports = {
changeNameAction,
addNumberAction
}
然后在使用的组件中进行调用
javascript
const store = require("./store")
const { addNumberAction, changeNameAction } = require("./store/actionCreators")
const unsubscribe = store.subscribe(() => {
console.log("订阅数据的变化:", store.getState())
})
// 修改store中的数据: 必须action
store.dispatch(changeNameAction("kobe"))
store.dispatch(changeNameAction("lilei"))
store.dispatch(changeNameAction("james"))
unsubscribe()
// 修改counter
store.dispatch(addNumberAction(10))
store.dispatch(addNumberAction(20))
store.dispatch(addNumberAction(30))
最终,通过拆分代码我们会形成4个文件:
- store/index.js文件
- store/reducer.js文件
- store/actionCreators.js文件
- store/constants.js文件
React中使用Redux
redux使用过程:首先会在一个中心的store里面存储我们对应的状态,然后就可以让一些组件中store中订阅一些数据;然后也可以在组件中通过dispatch来派发一些action,这些action就会到达Reducer里面,它就会自动执行该函数,并返回一个新的state对象,再根据新的state来更新数据。数据更新后就会自动告诉订阅者,我现在数据发生改变了,需要拿新数据,界面再重新渲染

step1:创建一个项目并安装redux
step2:创建store


step3:在组件中使用
javascript
import React, {PureComponent } from 'react'
import Home from './pages/Home'
import Profile from './pages/profile'
import "./style.css"
import store from './store'
export class App extends PureComponent {
constructor() {
super()
this.state = {
count: store.getState().count
}
}
componentDidMount() {
// 订阅store
store.subscribe(() => {
const state = store.getState()
this.setState({
count: state.count
})
})
}
render() {
const {count} = this.state
return (
<div>
<h2>App Count: {count}</h2>
<div className="pages">
<Home />
<Profile />
</div>
</div>
)
}
}
export default App
React-Redux
redux官方帮助我们提供了 react-redux 库,可简化在react中使用redux的过程
npm i react-redux
yarn add react-redux
Provider
在src/index.js中导入Provider,并包裹根组件→将Redux的store传递给整个应用程序→使得所有组件可访问Redux的状态
javascript
import React from 'react';
import ReactDOM from 'react-dom/client';
import App from './App';
import { Provider } from 'react-redux';
import store from './store';
const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
<React.StrictMode>
<Provider store={store}>
<App />
</Provider>
</React.StrictMode>
);
connect
connect是React-redux提供的一个高阶组件(HOC),用于将React组件与Redux的仓库联系起来;
它不会修改原始组件,而是返回一个新的、连接了Redux的组件
作用:
将Redux的状态(state ) 和(dispatch )映射到组件的props中
通过 mapStateToProps 和 mapDispatchToProps,可以自定义组件需要的状态和操作
javascript
import axios from "axios"
import * as actionTypes from "./constants"
export const calcNumber = (num) => {
return {type:actionTypes.CALC_NUMBER,num}
}
javascript
import React, { PureComponent } from 'react'
import { connect } from 'react-redux'
import { calcNumber } from '../store/actionCreators'
export class About extends PureComponent {
calcNumber(num) {
this.props.calcNumber(num)
}
render() {
const {count,banners, recommends} = this.props
return (
<div>
<h2>About:{count}</h2>
<button onClick={e => this.props.calcNumber(6)}>+6</button>
<button onClick={e => this.props.calcNumber(-6)}>-6</button>
<button onClick={e => this.props.calcNumber(10)}>+10</button>
<button onClick={e => this.props.calcNumber(-5)}>-5</button>
<div className="banners">
<h2>轮播图数据:</h2>
<ul>
{
banners.map(item => {
return <li key={item.acm}>
{item.title}
</li>
})
}
</ul>
</div>
<div className="recommend">
<h2>推荐数据</h2>
<ul>
{
recommends.map(item => {
return <li key={item.acm}>
{item.title}
</li>
})
}
</ul>
</div>
</div>
)
}
}
function mapStateToProps(state){
return {
count: state.count,
banners:state.banners,
recommends:state.recommends
}
}
const mapDispatchToProps = (dispatch) => {
return {
calcNumber(num) {
dispatch(calcNumber(num))
}
}
}
// connect()返回值是一个高阶组件
export default connect(mapStateToProps,mapDispatchToProps)(About)
组件中进行异步操作
网络请求可以在class组件的componentDidMount中发送

store/home.js
javascript
import axios from "axios"
import * as actionTypes from "./constants"
export const changeBanners = (banners) => {
return {type:actionTypes.CHANGE_BANNERS,banners}
}
export const changeRecommends = (recommends) => {
return {type:actionTypes.CHANGE_RECOMMENDS,recommends}
}
Home.jsx
javascript
import React, { PureComponent } from 'react'
import { connect } from 'react-redux'
import axios from 'axios'
import { changeBanners, changeRecommends } from '../store/actionCreators'
export class Category extends PureComponent {
componentDidMount() {
axios.get("http://123.207.32.32:8000/home/multidata").then(res => {
const banners = res.data.data.banner.list
const recommends = res.data.data.recommend.list
this.props.changeBanners(banners)
this.props.changeRecommends(recommends)
})
}
render() {
return (
<div>
<h2>Category Page:</h2>
</div>
)
}
}
const mapDispatchToProps = (dispatch) => {
return {
changeBanners(banners) {
dispatch(changeBanners(banners))
},
changeRecommends(recommends) {
dispatch(changeRecommends(recommends))
}
}
}
export default connect(null,mapDispatchToProps)(Category)
redux中进行异步操作
网络请求的数据也属于状态管理的一部分,我们最好还是将它放在redux中来管理

在默认情况下,dispatch(action)中传入的是一个对象→可通过reduc-thunk让dispatch中传入一个action函数
step1:安装redux-thunk
npm i redux-thunk
step2:在创建store时传入应用了middleware的enhance函数
- 通过applyMiddleware来结合多个Middleware, 返回一个enhancer;
- 将enhancer作为第二个参数传入到createStore中;
javascript
import { createStore,applyMiddleware } from "redux";
import {thunk} from "redux-thunk"
import reducer from "./reducer";
// 正常情况下,store.dispatch(object) 只能派发一个对象
// 想要派发函数store.dispatch(function) 需要做一个增强
const store = createStore(reducer,applyMiddleware(thunk))
export default store
step3:定义返回一个函数的action
javascript
import axios from "axios"
import * as actionTypes from "./constants"
export const changeBanners = (banners) => {
return {type:actionTypes.CHANGE_BANNERS,banners}
}
export const changeRecommends = (recommends) => {
return {type:actionTypes.CHANGE_RECOMMENDS,recommends}
}
export const fetchHomeMultidataAction = () => {
// 如果是一个普通的action,那么我们需要返回一个对象
// 问题:对象中不能直接拿到从服务器请求的数据
// return {}
return function(dispatch,getState) {
// 异步操作:网络请求
axios.get("http://123.207.32.32:8000/home/multidata").then(res => {
const banners = res.data.data.banner.list
const recommends = res.data.data.recommend.list
// dispatch({type:actionTypes.CHANGE_BANNERS,banners})
// dispatch({type:actionTypes.CHANGE_RECOMMENDS,recommends})
dispatch(changeBanners(banners))
dispatch(changeRecommends(recommends))
})
}
}
step4:在组件中进行派发
javascript
import React, { PureComponent } from 'react'
import { connect } from 'react-redux'
import { fetchHomeMultidataAction } from '../store/actionCreators'
export class Category extends PureComponent {
componentDidMount() {
this.props.fetchHomeMultidata()
}
render() {
return (
<div>
<h2>Category Page:</h2>
</div>
)
}
}
const mapDispatchToProps = (dispatch) => {
return {
fetchHomeMultidata() {
dispatch(fetchHomeMultidataAction())
}
}
}
export default connect(null,mapDispatchToProps)(Category)
Redux模块拆分
在开发中,如果将所有的数据都存储在一个state中,随着数据越来越多,会难以管理与维护;
我们可以对其进行模块的拆分

combineReducers底层原理
redux给我们提供了一个combineReducers函数可以方便的让我们对多个reducer进行合并
实现原理:
- 将我们传入的reducers合并到一个对象中,最终返回一个combination函数
- 在执行combination函数的过程中,会通过判断前后返回的数据是否相同来决定返回之前的state还是新的state
- 新的state会触发订阅者发生对应的刷新,而旧的state可以有效的组织订阅者发生刷新
javascript
// 实现原理
function reducer(state={},action) {
// 返回一个对象,作为store的状态
return {
count:counterReducer(state.count,action),
home:homeReducer(state.home,action),
user:userReducer(state.user,action)
}
}
Redux Toolkit(RTK)
简介
它封装了Redux的核心API,并提供了一些额外工具和约定,帮助我们更高效编写Redux代码
安装:
npm install @reduxjs/toolkit react-redux
核心API:
- configureStore:它自动配置了 Redux 的
createStore
和applyMiddleware
,并预装了一些常用的中间件(如redux-thunk
和redux-devtools-extension
) - createSlice:接受reducer函数的对象、切片名称和初始状态值,并自动生成切片reducer,并带有相应的actions
- createAsyncThunk:接受一个动作类型字符串和一个返回承诺的函数,并生成一个pending/fulfilled/rejected基于该承诺分派动作类型的 thunk
基本使用
1.configureStore创建大仓库store
javascript
import { configureStore } from "@reduxjs/toolkit";
import counterReducer from "./modules/counter";
const store = configureStore({
reducer: {
count: counterReducer,
},
});
export default store;
2.createSlice创建小仓库
javascript
import { createSlice } from "@reduxjs/toolkit";
const counterSlice = createSlice({
name: "counter",
initialState: {
count: 100
},
reducers: {
increment: (state, action) => {
state.count += action.payload;
},
decrement: (state, action) => {
state.count -= action.payload;
}
}
})
export const{increment, decrement} = counterSlice.actions
export default counterSlice.reducer;
3.将模块的reducer导入大仓库中
4.在组件中使用数据------还是和之前一样(Provider、connect)
异步使用
1.使用 createAsyncThunk 创建异步操作
- 在
createSlice
中处理异步操作的结果
javascript
import { createSlice, createAsyncThunk } from "@reduxjs/toolkit";
import axios from "axios";
export const fetchHomeMultidataAction = createAsyncThunk(
"home/multidata",
async () => {
const res = await axios.get("http://123.207.32.32:8000/home/multidata");
// 返回结构,那么action状态就会变成fulfilled状态
return res.data;
});
const homeSlice = createSlice({
name: "home",
initialState: {
banners: [],
recommends: []
},
reducers: {
changeBanners(state, { payload }) {
state.banners = payload;
},
changeRecommends(state, { payload }) {
state.recommends = payload;
}
},
extraReducers: (builder) => {
builder
.addCase(fetchHomeMultidataAction.pending, (state, action) => {
console.log("fetchHomeMultidataAction pending");
})
.addCase(fetchHomeMultidataAction.fulfilled, (state, action) => {
console.log("fetchHomeMultidataAction fulfilled");
// 这里的数据不需要浅拷贝------因为内部的ImmutableJS重构了redux,并返回了一个新对象
state.banners = action.payload.data.banner.list;
state.recommends = action.payload.data.recommend.list;
})
.addCase(fetchHomeMultidataAction.rejected, (state, action) => {
console.log("fetchHomeMultidataAction rejected");
});
}
});
export const { changeBanners, changeRecommends } = homeSlice.actions;
export default homeSlice.reducer;
3.在组件中调用该函数即可------与原来使用一样