五、redux的使用

一、安装依赖

yarn add redux

二、项目配置

新建store文件夹
新建index.js文件
新建reducer.js文件

2-1创建store(容器),管理数据

//index.js

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

2-2创建reducer,接受action,重新计算state

//reducer.js

let defaultState = {
    msg:"react"
}
export default (state=defaultState,action)=>{
    return state
}

2-3在Home.js导入store(需要在那个组件中使用，就在那里导入)

import store from '../store'js
class Home extends Component {
    constructor(props) {
        super(props);
        this.state = getState();
    }
    ....
}

2-4Action

View发出的一个通知，要改变state

• 通过一个事件派发action

  1.创建一个ation,同时派发
  import React, { Component } from 'react';
  import store from '../store'
  class Home extends Component {
    constructor(props) {
        super(props);
        this.state = store.getState();
    }
    render() {
        return (
            <div>
                首页
                <button onClick={this.handleClick}>改变store</button>
            </div>
        );
    }
    handleClick=()=>{
        const action = {
            type:"btn_change",
            value:"复习redux"
        }
        store.dispatch(action)
    }
  }
  export default Home;

• store自动接收action,之后将action传递给reducer

• 在reducer改变state

let defaultState = {
    msg:"react"
}
//reducer可以接收state,但是不能直接修改state
export default (state=defaultState,action)=>{
    console.log(action)
    switch(action.type){
        case "btn_change":
            var newState = {...state};
            newState.msg = action.value;
            return newState;
        default:
            return state;
    }
}

订阅store的状态的改变，只要store改变，store.subscribe(fn),fn函数必然会执行

class Home extends Component {
    constructor(props) {
        ...
        store.subscribe(this.handleStoreChange);
    }
    ...
    handleStoreChange=()=>{
        console.log(1)
        this.setState(store.getState())
    }
}

三、基本概念

store 就是保存数据的地方,将store看成一个容器,一个应用只能有一个store
//如何生成一个store createStore

//store--index.js
import { createStore } from 'redux'
const defaultState = {
    msg:"react很不好用"
}
const reducer = (state=defaultState,action)=>{
    return state;
}
// createStore只能接收函数
let store = createStore(reducer);
export default store;

reducer 就是对state重新计算的过程就是reducer,reducer必须是函数

四、redux的调试

4-1应用商店安装redux

https://github.com/zalmoxisus/redux-devtools-extension

4-2配置

import { createStore } from 'redux'
import reducer from './reducer'
// createStore只能接收函数
let store = createStore(reducer,window.__REDUX_DEVTOOLS_EXTENSION__ && window.__REDUX_DEVTOOLS_EXTENSION__());
export default store;