Redux实现组合计数器的示例代码
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2022-03-16 22:58:06
redux是一种解决数据共享的方案
import {createstore} from 'redux';
import react from 'react'...
redux是一种解决数据共享的方案
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
三个计数器的数据只和由redux管理
动图演示
实现的源码如下
index.html
<!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reducer
function 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store
let 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!
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。