web开发中Redux实现组合计数器
Redux是一种解决资料共享的方案，也是很多从事web前端开发人的痛点之一。下面，就给大家分享web开发中Redux实现组合计数器的教程及程式码例项，一起来看看吧。
Redux实现组合计数器
Redux是一种解决资料共享的方案
import {createStore} from 'redux';
import React from 'react';
import ReactDOM from 'react-dom';
import {connect, createProvider} from 'react-redux'
// data
let allNum = {num :1000}
// 建立reducer, 名字的预设值为
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
}
}
// 建立store储存资料(传入处理函式reducer, 核心资料allNum)
let store = createStore(reducer, allNum)
console.log("初始化的资料为",store.getState('num'))
// 新增监听函式
store.subscribe(() => {console.log("监听函式发出:", 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 Hello World;}
}
ReactDOM.render(, document.getElementById("root"));
React和Redux组合使用
React元件, 有两个资料集, props和state
props表示外部传入元件的引数(资料由外部传入, 可以被外部更改)
state表示元件固有的属性(资料私有, 不可以被外部更改)
我们可以把多个React元件的props交由Redux进行管理, 这样就实现了React元件之间资料的共享
元件如何读写资料
元件通过action传送讯号, reducer处理action, story内的值被reducer修改, 由于React元件已经被系结到story中, 所以story内的资料被修改后, 可以直接同步到React的元件中
小案例: 实现一个组合计数器
单个计数器的资料由元件自身state管理
三个计数器的资料只和由Redux管理
动图演示
实现的源代码如下
index.html
react-webpack-demo
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 (
计数器
元件值的和为: { this.props.sum }
)
}
}
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 (
{ value }
)
}
}
// 建立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 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
})
// 建立store
let store = createStore(reducer)
// connect连线
Counter = connect(CounterMapStateToProps, mapDispatchToProps)(Counter)
ManageCounter = connect(ManageCounterMapStateToProps, mapDispatchToProps)(ManageCounter)
ReactDOM.render(
,
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式供我们呼叫, 所以面对一个问题时, 我们考虑的重点是: React元件内哪些资料需要被Redux管理?把重点问题考虑清楚, 问题也就解决了大半!关注“武汉千锋”微信公众号，获取更多web前端学习资料！
