react-redux使用

 1.创建store文件夹，分别创建子文件夹actions和reducers

2。创建constant.js

/* 
    该模块是用于定义action对象中type类型的常量值，目的只有一个：便于管理的同时防止程序员单词写错
*/
export const CHANGEVALUE = 'change_value'

3.store.js

import { legacy_createStore as createStore, applyMiddleware } from "redux";
import thunk from "redux-thunk";
import reducers from "./reducers";
 
export default createStore(reducers, applyMiddleware(thunk))

4.reducers创建index.js和redux_test.js

redux_test.js

import { CHANGEVALUE } from "../constant";
 
//定义一个默认状态
const defaultState = {
    msg: "你好，世界"
}
 
//导出一个函数
// eslint-disable-next-line import/no-anonymous-default-export
export default (state = defaultState, action) => {
    //从action对象中获取：type、data
    const { type, data } = action
    let newState = JSON.parse(JSON.stringify(state))//使用深拷贝，不然数据不变化
    switch (type) {
        case CHANGEVALUE:
            newState.msg = state.msg + data;
            break
        default:
            break
    }
    return newState
}

index.js

/*
    该文件用于汇总所有的reducer为一个总的reducer
*/
 
//引入combineReducers，用于汇总多个reducer
 
import { combineReducers } from 'redux'
 
import redux_test from './redux_test'
 
 
 
//汇总所有的reducer变为一个总的reducer
 
export default combineReducers({
 
    redux_test
 
})

5.reducers创建redux_test.js

import { CHANGEVALUE } from "../constant"
 
/* 
    该文件专门为Count组件生成action对象
*/
//同步action，就是指action的值为Object类型的一般对象
export const changeValue = data => ({ type: CHANGEVALUE, data })

测试=====

index.js使用Provider监听redux，传入store

import React from 'react';
import ReactDOM from 'react-dom/client';
import { Provider } from 'react-redux';//redux
import App from './App';
import store from './store/store';
 
const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
  /* 此处需要用Provider包裹App，目的是让App所有的后代容器组件都能接收到store */
  <Provider store={store}>
    <App />
  Provider>
);

 所有使用redux的组件放在containers目录下

创建ReduxTest组件，redux父组件与子组件使用connect连接

import React, { Fragment } from 'react'
import { connect } from 'react-redux'
import { changeValue } from '../../store/actions/redux_test'
 
function ReduxTest(props) {
    return (
        <Fragment>
            <div>
                {props.msg}
            div>
            <button onClick={() => props.changeValue('----->hello')}>修改显示button>
        Fragment>
    )
}
//使用connect()()创建并暴露一个Count的容器组件
export default connect(
    state => ({
        msg: state.redux_test.msg
    }),
    {
        changeValue
    }
)(ReduxTest)