dispatch 的代理工作

src/ThemeSwitch.js 中,ThemeSwitch 组件通过 store 的 dispatch 方法实现了数据的更改,这也导致了组件的强耦合。

我们的思路是让高阶组件 Connect 代替 ThemeSwitch 来实现 dispatch 功能,同时通过 props 将方法传递给 ThemeSwitch 组件。

修改 src/react-redux.js文件:

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export const connect = (mapState2Props, mapDispatch2Props)=>(OriginComponent)=>{
class Connect extends Component {

componentWillMount(){
this._updateProps()
}

_updateProps(){
const {store} = this.context

let stateProps = mapState2Props? mapState2Props(store.getState(), this.props) : {}
let dispatchProps = mapDispatch2Props? mapState2Props(store.dispatch, this.props) : {}

this.setState({
allProps: {
...stateProps,
...dispatchProps,
...this.props
}
})
// 绑定订阅者监听函数
store.subscribe(this._updateProps.bind(this))
}
/*以下代码略*/
}

定义 mapDispatch2Props 函数

src/ThemeSwitch.js 文件中定义 mapDispatch2Props 函数:

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

class ThemeSwitch extends Component {
static propTypes = {
themeColor: PropTypes.string,
handleThemeSwitchClick: PropTypes.func
}

render() {
return (
<div>
<button
style={{color: this.props.themeColor}}
onClick={this.props.handleThemeSwitchClick.bind(this, 'red')}
>Red</button>
<button
style={{color: this.props.themeColor}}
onClick={this.props.handleThemeSwitchClick.bind(this, 'blue')}
>Blue</button>
</div>
)
}
}

const mapState2Props = (state)=>{
return {
themeColor: state.themeColor
}
}

const mapDispatch2Props = (dispatch)=>{
return {
handleThemeSwitchClick : function(color){
dispatch({
type: 'CHANGE_COLOR',
themeColor: color
})}
}
}

ThemeSwitch = connect(mapState2Props, mapDispatch2Props)(ThemeSwitch)

export default ThemeSwitch;

这样 ThemeSwitch 组件的代码就变得非常整洁,而且扩展性也大大提高。