wordpress 双语站点,wordpress 微信咨询菜单,济南网站建设公司川芎网络,遵义网站建设制作一、简介 react中的状态只属于某个组件。而Redux是一个全局管理js状态的架构#xff0c;让组件通信更加容易。 之前是状态在所有组件间传递#xff0c;而redux通过store来实现这个功能。
Redux特性#xff1a;
1.Single source Of truth#xff0c;通过store唯一维护状态…一、简介 react中的状态只属于某个组件。而Redux是一个全局管理js状态的架构让组件通信更加容易。 之前是状态在所有组件间传递而redux通过store来实现这个功能。
Redux特性
1.Single source Of truth通过store唯一维护状态。
2.可预测性state action - new state
3.纯函数更新store (纯函数 - 输入决定输出)
举个例子: 待办事项表
function todos(state [], action){switch(action.type){case ADD_TODO:return state.concat([{text: action.text, completed: false}]);case TOGGLE_TODO:return state.map((todo, idx) {action.index idx ? {text: todo.text, completed: !toto.completed}: todo})default:return state}}
二、核心概览 拿上图举个例子前端ui产生了deposit和withdraw2个事件store通过dispatcher分发对应的事件给reducer处理reducer处理后更新state。前端ui根据state重新渲染。
1.store
Redux的状态机实现store 通过state存储状态通过dispatch传播事件通过Reducer处理事件。
2.action action表示变更事件。一般包含event type 和 context。
3.Reducer reducer是状态事件处理。
举个例子: 待办事项表
function todoApp(state initialState, action){switch (action.type){case ADD_TODO:return Object.assign({}, state, {todos:[...state.todos,{text: action.text,completed: false}]});default:return state;}
}
三、使用示例
用redux实现一个简单计数器包括增加、减少功能。
import React from react;
import {createStore} from redux;
function run(){// store initial stateconst initialState { count: 0};// reducerconst counter (state initialState, action) {switch (action.type){case PLUS_ONE:return {count: state.count 1};case MiNUS_ONE:return {count: state.count - 1};case CUSTOM_COUNT:return {count: state.count action.payload.count};default:return state;} }// create storeconst store createStore(counter);// Action creatorfunction plusOne(){return {type: PLUS_ONE}}function minusOne(){return {type: MINUS_ONE};}function customCount(count){return {type: CUSTOM_COUNT, payload:{count}};}// 订阅redux 状态变更store.subscribe(() console.log(store.getState()));store.dispatch(plusOne());store.dispatch(minusOne());store.dispatch(customCount(5));
}export default () {divbutton onClick{run}Run/buttonp* 请打开控制台查看运行结果/p/div
}
bindActionCreators使用,工具类可以减少显示dispatch操作
import React from react;
import {createStore, bindActionCreators} from redux;
function run(){// store initial stateconst initialState { count: 0};// reducerconst counter (state initialState, action) {switch (action.type){case PLUS_ONE:return {count: state.count 1};case MiNUS_ONE:return {count: state.count - 1};case CUSTOM_COUNT:return {count: state.count action.payload.count};default:return state;} }// create storeconst store createStore(counter);// Action creatorfunction plusOne(){return {type: PLUS_ONE}}function minusOne(){return {type: MINUS_ONE};}function customCount(count){return {type: CUSTOM_COUNT, payload:{count}};}plusOne bindActionCreators(plusOne, store.dispatch);minusOne bindActionCreators(minusOne, store.dispatch);customCount bindActionCreators(customCount, store.dispatch);// 订阅redux 状态变更store.subscribe(() console.log(store.getState()));plusOne();minusOne();customCount(5);
}export default () {divbutton onClick{run}Run/buttonp* 请打开控制台查看运行结果/p/div
}
四、结合React使用
使用Connect功能将redux的action和state作为props传递给组件。
计数器组件使用样例
import React from react;
import {createStore, bindActionCreators} from redux;
import {Provider, connect} fomr react-redux;// store initial state
const initialState {count: 0};// reducer
const counter (state initialState, action) {switch (action.type){case PLUS_ONE:return {count: state.count 1};case MiNUS_ONE:return {count: state.count - 1};case CUSTOM_COUNT:return {count: state.count action.payload.count};default:return state;}
}
// create store
const store createStore(counter);
// Action creator
function plusOne(){return {type: PLUS_ONE}
}
function minusOne(){return {type: MINUS_ONE};
}export class Counter extends React.Component{render(){const {count, plusOne, minusOne} this.props;return (div className counterbutton onClick {minusOne}-/buttonspan{count}/spanbutton onClick {plusOne}/button/div);}
}// 将store的state与组件props绑定
function mapStateToProps(state){return {count: state.count};
}// 将store的action与组件props绑定
function mapDispatchToProps(dispatch){return bindActionCreators({plusOne, minusOne}, dispatch)
}// 通过connect组件将store与counter组件关联
const ConnectedCounter connect(mapStateToProps, mapDispatchToProps)(Counter) ;// 返回使用样例
export default class CounterSample extends React.Component{render(){return (// prodiver 基于react context实现可以让里面的子组件都能获取到storeProvider store {store}ConnectedCounter//Provider);}
}
