入到第四期，

代码大大简化，

但如果没有前面的演化过程，

一定让人蒙圈~~

三个主要文件：

index.js

import React from 'react';
import ReactDOM from 'react-dom';
import {Provider} from 'react-redux';

import './index.css';

import ControlPanel from './views/ControlPanel';
import store from './Store';

import registerServiceWorker from './registerServiceWorker';

ReactDOM.render(
	<Provider store={store}>
		<ControlPanel />
	</Provider>,document.getElementById('root'));
registerServiceWorker();

Counter.js

import React,{ Component } from 'react';
import PropTypes from 'prop-types';
import {connect} from 'react-redux';

import * as Actions from '../Actions.js';

const buttonStyle = {
	margin: '10px'
};

const propTypes  = {
	caption: PropTypes.string.isrequired
};

function Counter({caption,onIncrement,onDecrement,value}){
	return (
		<div>
			<button style={buttonStyle} onClick={onIncrement}>+</button>
			<button style={buttonStyle} onClick={onDecrement}>-</button>
			<span> { caption }  count: {value}</span>
		</div>
	);

}

Counter.propTypes  = {
	caption: PropTypes.string.isrequired,onIncrement: PropTypes.func.isrequired,onDecrement: PropTypes.func.isrequired,value: PropTypes.number.isrequired
};

function mapStateToProps(state,ownProps) {
	return {
		value: state[ownProps.caption]
	}
}

function mapDispatchToProps(dispatch,ownProps) {
	return {
		onIncrement: () => {
			dispatch(Actions.increment(ownProps.caption));
		},onDecrement: () => {
			dispatch(Actions.decrement(ownProps.caption));
		}
	}
}



export default connect(mapStateToProps,mapDispatchToProps)(Counter);

Summary.js

import React,{Component} from 'react';
import PropTypes from 'prop-types';
import {connect} from 'react-redux';

function Summary ({value}) {
	return (
		<div>Total Count: {value}</div>
	);
}

Summary.propTypes  = {
	value: PropTypes.number.isrequired
};


function mapStateToProps(state){
	let sum = 0;
	for (const key in state) {
		if (state.hasOwnProperty(key)) {
			sum += state[key];
		}
	}
	return {value: sum};
}


export default connect(mapStateToProps)(Summary);