Redux是一种解决数据共享的方案
Redux修改数据的简单案例
import {createStore} from 'redux';import React from 'react';import ReactDOM from 'react-dom';import {connect, createProvider} from 'react-redux'
// data
let allNum = {num :1000}
// 创建reducer, 名字的默认值为
function reducer(state, action) {
let tmp = {}
if (action.type == "decrease"){
allNum.num = allNum.num - action.value;
tmp = Object.assign({}, state, {num: allNum.num})
return tmp
}else if(action.type == "increase"){
allNum.num = allNum.num + action.value;
tmp = Object.assign({}, state, {num: allNum.num})
return tmp
}else{
return state
}
}
// 创建store存储数据(传入处理函数reducer, 核心数据allNum)
let store = createStore(reducer, allNum)
console.log("初始化的数据为",store.getState('num'))
// 添加监听函数
store.subscribe(() => {console.log("监听函数发出:", store.getState())});
// 发出action
let tmp = {};
tmp = store.dispatch({type: "decrease", value: 10})
console.log("---->", tmp);
tmp = store.dispatch({type: "decrease", value: 100})
console.log("---->", tmp);
tmp = store.dispatch({type: "increase", value: 31})
console.log("---->", tmp);
tmp = store.dispatch({type: "increase", value: 123})
console.log("---->", tmp);
class MyComponent extends React.Component {
render() {return <div>Hello World</div>;}
}
ReactDOM.render(<MyComponent />, document.getElementById("root"));
## React和Redux组合使用- React组件, 有两个数据集, `props`和`state` - `props`表示外部传入组件的参数(数据由外部传入, 可以被外部更改)- `state`表示组件固有的属性(数据私有, 不可以被外部更改)- 我们可以把多个React组件的`props`交由Redux进行管理, 这样就实现了React组件之间数据的共享> ## 组件如何读写数据> 组件通过action发送信号, reducer处理action, story内的值被reducer修改, 由于React组件已经被绑定到story中, 所以story内的数据被修改后, 可以直接同步到React的组件中> ## 小案例: 实现一个组合计数器- 单个计数器的数据由组件自身state管理- 三个计数器的`数据之和`由Redux管理> - 实现的源码如下#### index.html```js <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>react-webpack-demo</title> </head> <body> <div id="root"></div> </body> </html>
index.js
import 'babel-polyfill';import React from 'react';import ReactDOM from 'react-dom';import './index.scss';import Redux from 'redux';import { connect, Provider } from 'react-redux';import { createStore } from 'redux';import { PropTypes } from 'prop-types';class ManageCounter extends React.Component {
constructor(props) {
super(props);
}
render() {
return ( <div>
<p className="title">计数器</p>
<Counter id = "0" />
<Counter id = "1" />
<Counter id = "2" />
<p className="result"> 组件值的和为: { this.props.sum } </p>
</div> )
}}class Counter extends React.Component {
constructor(props) {
super(props);
this.changeSum = this.changeSum.bind(this)
this.decrease = this.decrease.bind(this)
this.increase = this.increase.bind(this)
this.state = { value: 0 };
}
changeSum() {
this.props.dispatch({ type: 'changeSum', payload: { id: this.props.id, value: this.state.value } })
}
decrease() {
let self = this;
this.setState({ value: this.state.value - 1 }, () => {
self.changeSum()
})
}
increase() {
let self = this;
self.setState({ value: this.state.value + 1 }, () => {
self.changeSum()
})
}
render() {
const { value } = this.state;
let { id } = this.props;
return ( <div >
<input type = "button"value = "减1" onClick = { this.decrease }/>
<span > { value } < /span><br/ >
<input type = "button" value = "加1" onClick = { this.increase }/>
</div> )
}
}
// 创建reducerfunction reducer(state = { number: [0, 0, 0], sum: 0 }, action = {}) {
if (action.type == 'changeSum') {
let { id, value } = action.payload
console.log("id:", id, "value:", value);
state.number[id] = value
let tmpSum = 0;
for (let i = 0; i < state.number.length; i++) {
tmpSum += state.number[i]
}
return Object.assign({}, state, { sum: tmpSum });
} else {
return state;
}}const CounterMapStateToProps = (state) => ({})const ManageCounterMapStateToProps = (state) => ({
sum: state.sum})const mapDispatchToProps = (dispatch) => ({
dispatch: dispatch})// 创建storelet store = createStore(reducer)// connect连接Counter = connect(CounterMapStateToProps, mapDispatchToProps)(Counter)ManageCounter = connect(ManageCounterMapStateToProps, mapDispatchToProps)(ManageCounter)ReactDOM.render(
<Provider store = { store }>
<ManageCounter />
</Provider> ,
document.getElementById('root'));index.scss
$designWidth: 750;@function px2rem($px) {
@return $px*10/$designWidth+rem;}#root {
div {
p {
font-size: px2rem(300);
color: #5EA1F3;
text-align: center;
}
div {
font-size: px2rem(500);
display: flex;
color: #64B587;
border: 1px solid #F0BB40;
input {
flex: 1 1 auto;
background-color: #64B587;
font-size: px2rem(200);
outline: none;
color:#ffffff;
}
span {
width: 300px;
flex: 1 1 auto;
text-align: center;
}
}
.title {
color: #BDBDBD;
}
.result {
font-size: px2rem(200);
}
}}小结
redux的设计思想是很简单的, 也有了很成熟的库函数供我们调用, 所以面对一个问题时, 我们考虑的重点是: React组件内哪些数据需要被Redux管理?把重点问题考虑清楚, 问题也就解决了大半!
上面已经把内容写完了, 但不到200个字符不让发布, 所以再凑点字数...
学习Redux感到困难往往不是Redux本身有多难, 而是, 过早接触了一些封装好的的配套函数库, 而配套的函数库的文档也很蛋疼, 很难一遍读懂, 如果不能读第二遍, 就直接从入门到放弃了
初见React时, 感觉Action, Reducer, Story的概念挺新颖, 但慢慢接触后发现, Aciton就是一个参数集合, Reducer就是一个处理Action的函数, Story就是一个数据集, 这样就变得很容易了
原创首发于慕课网
源码GitHub地址: https://github.com/zhaoolee/react-redux-counter
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