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vue（redux专场、hook（useState、useEffect、useReducer）、context）框架_vue context

作者：数据灵魂 | 2024-01-30 21:13:29

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vue context

知识点收尾为项目开始

知识点

redux专场

帮助react维护状态数据

verson 1

//redux/index.js
import {createStore} from 'redux'

function PersionReducer(stata=[],action){
    switch(action.type){
        case 'insert':
            break
        case 'select':
            break
        case 'update':
            break
        case 'delete':
            break
        default:
            return state
    }
}

const store = createStore(PersionReducer)

export default store
//调用
import store from './reudx'

store.getState()
store.dispatch({type: 'inser', data: obj})

version 2

多个数据进行识别

//redux/index.js
import {createStore} from 'redux'

function PersionReducer(stata=[],action){
    switch(action.type){
        case 'person/insert':
            break
        case 'person/select':
            break
        case 'person/update':
            break
        case 'person/delete':
            break
        case 'goods/insert':
            break
        default:
            return state
    }
}

const store = createStore(PersionReducer)

export default store
//调用
import store from './reudx'

store.getState()
store.dispatch({type: 'person/inser', data: obj})

version 3

变量整合

version 3.1

//redux/index.js
import {createStore} from 'redux'

export const InsertAction = data=>{type: 'person/insert', data: obj}
export const UpdateAction = data=>{type: 'person/update', data: obj}
export const DeleteAction = data=>{type: 'person/delete', data: obj}
export const SelectAction = data=>{type: 'person/select', data: obj}


function PersionReducer(stata=[],action){
    switch(action.type){
        case 'person/insert':
            break
        case 'person/select':
            break
        case 'person/update':
            break
        case 'person/delete':
            break
        default:
            return state
    }
}

const store = createStore(PersionReducer)

export default store
//调用
import store from './reudx'
import {InsertAction} from './reudx'
store.getState()
store.dispatch(InsertAction(data))

version 3.2

//redux/index.js
import {createStore} from 'redux'
const InsertType = 'person/inser'
const UpdateType = 'person/update'
const DeleteType = 'person/delete'
const SelectType = 'person/select'


export const InsertAction = data=>{type: InsertType, data: obj}
export const UpdateAction = data=>{type: UpdateType, data: obj}
export const DeleteAction = data=>{type: DeleteType, data: obj}
export const SelectAction = data=>{type: SelectType, data: obj}


function PersionReducer(stata=[],action){
    switch(action.type){
        case InsertType:
            break
        case SelectType:
            break
        case UpdateType:
            break
        case SelectType:
            break
        default:
            return state
    }
}

const store = createStore(PersionReducer)

export default store
//调用
import store from './reudx'
import {InsertAction} from './reudx'
store.getState()
store.dispatch(InsertAction(data))

version 4

代码拆分

//actionType.js

export const InsertType = 'person/inser'
export const UpdateType = 'person/update'
export const DeleteType = 'person/delete'
export const SelectType = 'person/select'

//action.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'
export const InsertAction = data=>{type: InsertType, data: obj}
export const UpdateAction = data=>{type: UpdateType, data: obj}
export const DeleteAction = data=>{type: DeleteType, data: obj}
export const SelectAction = data=>{type: SelectType, data: obj}

//reducer.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'

export default function PersionReducer(stata=[],action){
    switch(action.type){
        case InsertType:
            break
        case SelectType:
            break
        case UpdateType:
            break
        case SelectType:
            break
        default:
            return state
    }
}

//index.js
import {createStore} from 'redux'
import PersionReducer from './reducer'

const store = createStore(PersionReducer)

export default store

version 5

combineReducer 合并多个reducer

//actionType.js

export const InsertType = 'person/inser'
export const UpdateType = 'person/update'
export const DeleteType = 'person/delete'
export const SelectType = 'person/select'

//action.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'
export const InsertAction = data=>{type: InsertType, data: obj}
export const UpdateAction = data=>{type: UpdateType, data: obj}
export const DeleteAction = data=>{type: DeleteType, data: obj}
export const SelectAction = data=>{type: SelectType, data: obj}

//reducer.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'

export default function PersionReducer(stata=[],action){
    switch(action.type){
        case InsertType:
            break
        case SelectType:
            break
        case UpdateType:
            break
        case SelectType:
            break
        default:
            return state
    }
}

//index.js
import {createStore,combineReducer } from 'redux'
import PersionReducer from './reducer'

const store = createStore(combineReducer({
    persion: PersionReducer
    //goods: goods
}))

export default store

//调用
import store from './reudx'
import {InsertAction} from './reudx'
store.getState()
store.dispatch(InsertAction(data))

version 6

react-redux:解决在组件当中redux和业务逻辑代码混写的局面

npm i react-redux -S

使用步骤

1、在要使用的标签根部使用provider标签进行包围

2、使用connect将store当中的数据和方法绑定到action的props

//actionType.js

export const InsertType = 'person/inser'
export const UpdateType = 'person/update'
export const DeleteType = 'person/delete'
export const SelectType = 'person/select'

//action.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'
export const InsertAction = data=>{type: InsertType, data: obj}
export const UpdateAction = data=>{type: UpdateType, data: obj}
export const DeleteAction = data=>{type: DeleteType, data: obj}
export const SelectAction = data=>{type: SelectType, data: obj}

//reducer.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'

export default function PersionReducer(stata=[],action){
    switch(action.type){
        case InsertType:
            break
        case SelectType:
            break
        case UpdateType:
            break
        case SelectType:
            break
        default:
            return state
    }
}

//index.js
import {createStore,combineReducer } from 'redux'
import PersionReducer from './reducer'

const store = createStore(combineReducer({
    persion: PersionReducer
    //goods: goods
}))

export default store

//调用
//App.js
import store from './redux/index.js'
<provider store={store}>
    <Persion></Presion>
</provider>

//Persion.jsx
import {connect} from 'react-redux'
import {InsertAction} from './reudx'

class Persion extends react.Component{
    UNSAFE_componentWillMount(){
        this.props.persionAction()
        console.log(this.props.persion)
    }
    .....
}
.....
const 绑定state数据的回调函数 = (state)=>{
    //自动接受的store下的state数据
    return {
        persion: state.persion
    }
}

const 绑定action操作的回调函数 = (dispatch)=>{
    persionAction: data=>dispath(InsertAction(data))
}
export default connect(绑定state数据的回调函数,绑定action操作的回调函数)(Persion)

version 6.1

bindActionCreators动态绑定action方法

//actionType.js

export const InsertType = 'person/inser'
export const UpdateType = 'person/update'
export const DeleteType = 'person/delete'
export const SelectType = 'person/select'

//action.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'
export const InsertAction = data=>{type: InsertType, data: obj}
export const UpdateAction = data=>{type: UpdateType, data: obj}
export const DeleteAction = data=>{type: DeleteType, data: obj}
export const SelectAction = data=>{type: SelectType, data: obj}

//reducer.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'

export default function PersionReducer(stata=[],action){
    switch(action.type){
        case InsertType:
            break
        case SelectType:
            break
        case UpdateType:
            break
        case SelectType:
            break
        default:
            return state
    }
}

//index.js
import {createStore,combineReducer } from 'redux'
import PersionReducer from './reducer'

const store = createStore(combineReducer({
    persion: PersionReducer
    //goods: goods
}))

export default store

//调用
//App.js
import store from './redux/index.js'
<provider store={store}>
    <Persion></Presion>
</provider>

//Persion.jsx
import {connect} from 'react-redux'
*********import * as actions from './reudx'
*********import {bindActionCreators} from 'redux'


class Persion extends react.Component{
    UNSAFE_componentWillMount(){
        this.props.persionAction()
        console.log(this.props.persion)
    }
    .....
}
.....
const 绑定state数据的回调函数 = (state)=>{
    //自动接受的store下的state数据
    return {
        persion: state.persion
    }
}

*********const 绑定action操作的回调函数 = dispatch=>bindActionCreators(actions,dispatch)
export default connect(绑定state数据的回调函数,绑定action操作的回调函数)(Persion)

version 7

redux-thunk 异步任务

npm i redux-thunk -S

//actionType.js

export const InsertType = 'person/inser'
export const UpdateType = 'person/update'
export const DeleteType = 'person/delete'
export const SelectType = 'person/select'

//action.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'
export const InsertAction = data=>{type: InsertType, data: obj}
export const UpdateAction = data=>{type: UpdateType, data: obj}
export const DeleteAction = data=>{type: DeleteType, data: obj}
export const SelectAction = data=>{type: SelectType, data: data}
**********
export default AsyncPerion=()=>{
    return dispatch=>{
        axios.get(url).ther(res=>{
            if(res.code === 200){
                dispatch(SelectAction(res.list))
            }  
        })
    }
}
**********
//reducer.js
import {InsertType,UpdateType,DeleteType,SelectType} from './actionType'

export default function PersionReducer(stata=[],action){
    switch(action.type){
        case InsertType:
            break
        case SelectType:
            break
        case UpdateType:
            break
        case SelectType:
            break
        default:
            return state
    }
}

//index.js
**********import {createStore,combineReducer,applyMiddleware } from 'redux'
**********import {componentWithDevTools} from 'redux-devtools-extension'
**********import thunk from 'redux-thunk'

import PersionReducer from './reducer'

const store = createStore(combineReducer({
    persion: PersionReducer
    //goods: goods
**********}),componentWithDevTools(applyMiddleware(thunk)))

export default store

//调用
//App.js
import store from './redux/index.js'
<provider store={store}>
    <Persion></Presion>
</provider>

//Persion.jsx
import {connect} from 'react-redux'
import * as actions from './reudx'
import {bindActionCreators} from 'redux'


class Persion extends react.Component{
    UNSAFE_componentWillMount(){
        ***************this.props.AsyncPerion()
        this.props.persionAction()
        console.log(this.props.persion)
    }
    .....
}
.....
const 绑定state数据的回调函数 = (state)=>{
    //自动接受的store下的state数据
    return {
        persion: state.persion
    }
}

const 绑定action操作的回调函数 = dispatch=>bindActionCreators(actions,dispatch)
export default connect(绑定state数据的回调函数,绑定action操作的回调函数)(Persion)

反馈

不知道react-redux处理过的值（存在于<layout>props中的state和各种dispatch方法）能不能在往下传递，例如layout下面仍有子组件需要触发store.dispatch,该怎么写？（试过用组件父传子的方式，将layout的整个props作为属性值往下传递，但是子组件的props并未改变）

const 绑定state数据的回调函数 = (state)=>{
    console.log(state)
    //自动接受的store下的state数据
    return {
        persion: state.persion
    }
}

export default connect(绑定state数据的回调函数)(Persion)

hook

React – A JavaScript library for building user interfaces

Hook 简介 – React

react拥有两种组件，类组件和函数组件，其中函数组件默认没有生命周期和状态数据，hook填补了这个空缺。

Hook 是 React 16.8 的新增特性。它可以让你在不编写 class 的情况下使用 state 以及其他的 React 特性。

useState

没有状态数据的前提下，函数组件当中的数据修改后很难刷新

export default function layout(){
    var msg = 0
    const addMsg=()=>{
        msg++
        console.log(msg)
    }
    return <>
        <p>{msg}</p>
        <button onClick={addMsg}>加</button>
    </>
}

使用useState

1、定义useState方法，然后传入初始值

2、useState会返回两个参数，分别是state数据和可以刷新设置数据的方法

import React, { useState } from 'react';

export default function Layout(){
    const [count, setCount] = useState(0);
    const addMsg=()=>{
        setCount(count + 1)
    }
    return <>
        <p>{count}</p>
        <button onClick={addMsg}>加</button>
    </>
}

如果state是多个数据，必须都发生修改，否则，没有修改的数据被置空覆盖了

import React, { useState } from 'react';
import img from "../asserts/image/1.jpg"
export default function Layout(){
    const [count, setCount] = useState({isShow:1,title: "隐藏"});
    const toggle = ()=>{
        if(count.isShow){
            setCount({title: "显示"})
        }else{
            setCount({isShow:1,title: "隐藏"})
        }
        console.log(count)
        
    }
    return <>
        <p>
            {
                count.isShow===1?<img src={img} style={{width:"100px"}} />:""
            }
            
        </p>
        <button onClick={toggle}>{count.title}</button>
    </>
}

useEffect

作用: 可以让函数组件拥有自己的生命周期

useEffect会在组件第一次挂载完毕, 更新完毕, 组件即将卸载的时候自动触发,相当于类组件中componentDidMount , componentDidUpdate, componentWillUnmount三个钩子函数的集合

componentDidMount ：组件初始化挂载之后，执行useEffict当中的语句，不执行useEffict当中返回的函数
componentDidUpdate ：组件初始化挂载之后，先执行useEffict当中返回的函数，再执行useEffict当中的语句
componentWillUnmount：只执行useEffict当中返回的函数

import React, { useEffect,useState } from 'react';

export default function Home(){
    let [state,setState] = useState("我是home组件")
    useEffect(
        ()=>{
            var obj = document.querySelector("#home_id")
            console.log("我执行了",obj)
            return ()=>{
                console.log("我是home组件的嵌套函数，我执行了",obj)
            }//这个函数在组件卸载前执行
        }
    )
    const change = ()=>{
        setState("hello,我确实是home组件")
    }
    return <>
      <p id="home_id" onClick={change}>{state}</p>
    </>
}

useEffect在所有组件内数据发送修改都执行，这个不合适。

useEffect拥有两个参数

第一个参数是一个操作函数，包含两部分，执行的语句，和返回的函数
第二个参数是一个数组，数组的元素是要监听的变量

import React, { useEffect,useState } from 'react';

export default function Home(){
    let [state,setState] = useState("我是home组件")
    let [hhh,setHhh] = useState("hhhh")
    
    useEffect(
        ()=>{
            var obj = document.querySelector("#home_id")
            console.log("我执行了",obj)
            return ()=>{
                console.log("我是home组件的嵌套函数，我执行了",obj)
            }
        },[state]
    )
    const change = ()=>{
        setState("hello,我确实是home组件")
    }
    const changeHhh = ()=>{
        setHhh("哈哈哈")
    }
    
    return <>
      <p id="home_id" onClick={change}>{state}</p>
      <p id="home_id" onClick={changeHhh}>{hhh}</p>
      
    </>
}

useEffict返回的函数通常用来回收内容。

import React, { useEffect,useState } from 'react';
var timer = ""
export default function Home(){
    let [now,setTime] = useState(Date.now())
    useEffect(
        ()=>{
            return ()=>{
                clearInterval(timer)
                console.log("我是home组件的嵌套函数，我执行了")
            }
        },[]
    )
    const start= ()=>{
        timer = setInterval(()=>{
            setTime(Date.now())
        },1)
    } 
    const end=()=>{
        clearInterval(timer)
    }   
    return <>
        <p>{now}</p>
        <button onClick={start}>开始</button>
        <button onClick={end}>停止</button>
        
    </>
}

useReducer

作用: 可以让函数组件拥有自己的状态数据

参数1: 数据处理函数reducer
参数2: 数据默认值
返回值: 数组
- 第一个元素: 状态数据对象
- 第二个元素: dispatch数据更新方法, dispatch可以发送一个数据操作对象action给数据处理函数reducer

代码如下：

import React, { useReducer } from 'react';

export default function Home() {
    const reducer = (state, action) => {
        var data = action.data
        switch (action.type) {
            case 'add':
                var obj = state + data
                return obj
            case 'cut':
                var objs = state - data
                return objs
            default:
                return state
        }
    }

    const [state, dispatch] = useReducer(reducer, 0)
    const change_add = () => {
        dispatch({type: 'add',data: 10})
    }
    const change_cut = () => {
        dispatch({type: 'cut',data: 5})
    }

    return <>
        <div style={{ width: "200px", margin: "0 auto" }}>
            <button onClick={change_add}>增加</button>
            <p>{state}</p>
            <button onClick={change_cut}>减少</button>
        </div>
    </>
}

context

在复杂的嵌套情况下，组件之间传参不能很方便，所以需要有一个之间可以传参的方法，就是context

生成消费者模式

consumer(消费者)

第一种写法：

1、导入myContext

2、使用<myContext.Consumer>标签

3、标签内部需要由一个函数接受myContext的数据

4、使用数据

import React, { Component } from 'react'
import '../asserts/css/base.css'
import Father from './Father'
import myContext from '../utils/context'

export default class Grandpa extends Component {
    state={
        msg: "先辈参数 abc"
    }
    render() {
        return (
            <div className="grandpa">
                我是先辈组件 --- 先辈参数 - {this.state.msg}
                <br/>
                <myContext.Consumer>
                    {
                        (context)=>{
                            console.log(context)
                            return <>
                                {
                                    context.list.map(item=>(
                                        <p key={item.id}>{item.name}</p>
                                    ))
                                }
                            </>
                        }
                    }
                </myContext.Consumer>
                <br/>
                
                <Father msg={this.state.msg}></Father>
            </div>
        )
    }
}

第二种写法：

import React, { Component } from 'react'
import '../asserts/css/base.css'
import Father from './Father'
import myContext from '../utils/context'

export default class Grandpa extends Component {
    state={
        msg: "先辈参数 abc"
    }
    static contextType = myContext //contextType固定写法
    render() {
        console.log(this.context)
        return (
            <div className="grandpa">
                我是先辈组件 --- 先辈参数 - {this.state.msg}
                <br/>
                    {
                        this.context.list.map(item=>(
                            <p key={item.id}>{item.name}</p>
                        ))
                    }
                <br/>
                
                <Father msg={this.state.msg}></Father>
            </div>
        )
    }
}

provider(生产者)

采用<myContext.Provider value={this.state.gList}>传递参数context

自行百度 老师没讲对

确实在子组件当中调用context的结果

项目开始

项目创建

创建项目库

创建项目

安装依赖

npm i events react-router-dom@5.2.0 axios -S

调整结构

修改端口

封装axios

import { Component } from 'react'
import axios from 'axios'

axios.defaults.baseURL ="/api"

axios.interceptors.response.use(response=>{
    return response.data
})

Component.prototype.$http = axios

export default axios

设置跨域

npm install --save-dev http-proxy-middleware@1.0

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