目标

react使用redux的主要目的是：
1）实现简洁统一的状态维护，提高代码可维护性；
2）实现简洁的注入依赖，避免重重传递参数；
Plug Any Data Into Any Component. This is the problem that Redux solves. It gives components direct access to the data they need.
3）实现自动化渲染。

index.js

应用的入口代码

import React from 'react';
import { render } from 'react-dom';
import Counter from './Counter';
import { Provider } from 'react-redux';
import { createStore } from 'redux';const initialState = {count: 0
};function reducer(state = initialState, action) {switch(action.type) {case 'INCREMENT':return {count: state.count + 1};case 'DECREMENT':return {count: state.count - 1};default:return state;}
}/**
* 1） 创建全局存储对象 store,传入合适的reducer.
*/
const store = createStore(reducer);/**
* 2） 将store实例绑定到 App
*/const App = () => (<Provider store={store}><Counter/></Provider>
);render(<App />, document.getElementById('root'));

组件代码

import React from 'react';
import { connect } from 'react-redux';/**
* index.js创建的store全局对象，会注入到所有下级对象中，因此这里才可以使用dispatch函数来改变属性。
*/
class Counter extends React.Component {increment = () => {//实际上是调用全局store对象的dispatch函数this.props.dispatch({ type: 'INCREMENT' });}decrement = () => {this.props.dispatch({ type: 'DECREMENT' });}render() {return (<div><h2>Counter</h2><div><button onClick={this.decrement}>-</button><span>{this.props.count}</span><button onClick={this.increment}>+</button></div></div>)}
}//具体的属性转换函数
function mapStateToProps(state) {return {count: state.count};
}//通过connect方法将store的state属性转换成本组件的属性
export default connect(mapStateToProps)(Counter);