react之自定义react-redux的providerconnect

Posted 2021-01-07 raind

Provider

// Provider把store放到context里，所有的子元素可以直接取到store
import React from ‘react‘
import PropTypes from ‘prop-types‘
import {bindActionCreators} from ‘./utils.js‘

export const connect = (mapStateToProps=state=>state,mapDispatchToProps={})=>(WrapComponent)=>{
    return class ConnectComponent extends React.Component{
        static contextTypes = {
            store:PropTypes.object
        }
        constructor(props, context){
            super(props, context)
            this.state = {
                props:{}
            }
        }
        componentDidMount(){
            const {store} = this.context
            store.subscribe(()=>this.update())
            this.update()
        }
        update(){
            const {store} = this.context
            const stateProps = mapStateToProps(store.getState())
            const dispatchProps = bindActionCreators(mapDispatchToProps, store.dispatch)
            this.setState({
                props:{
                    ...this.state.props,
                    ...stateProps,
                    ...dispatchProps    
                }
            })
        }
        render(){
            return <WrapComponent {...this.state.props}></WrapComponent>
        }
    }
}

export class Provider extends React.Component{
    static childContextTypes = {
        store: PropTypes.object
    }
    getChildContext(){
        return {store:this.store}
    }
    constructor(props, context){
        super(props, context)
        this.store = props.store
    }
    render(){
        return this.props.children
    }
}

utils.js

export function createStore(reducer, enhancer){
    if (enhancer) {
        return enhancer(createStore)(reducer)
    }
    let currentState = {}
    let currentListeners = []

    function getState(){
        return currentState
    }
    function subscribe(listener){
        currentListeners.push(listener)
    }
    function dispatch(action){
        currentState = reducer(currentState, action)
        currentListeners.forEach(v=>v())
        return action
    }
    dispatch({type:‘@IMOOC/WONIU-REDUX‘})
    return { getState, subscribe, dispatch}
}

// 自定义applyMiddleware函数
export function applyMiddleware(...middlewares){
    return createStore=>(...args)=>{
        const store = createStore(...args)
        let dispatch = store.dispatch

        const midApi = {
            getState:store.getState,
            dispatch:(...args)=>dispatch(...args)
        }
        const middlewareChain = middlewares.map(middleware=>middleware(midApi))
        dispatch = compose(...middlewareChain)(store.dispatch)
        return {
            ...store,
            dispatch
        }

    }
}
// 自定义compose函数
export function compose(...funcs){
    if (funcs.length==0) {
        return arg=>arg
    }
    if (funcs.length==1) {
        return funcs[0]
    }
    return funcs.reduce((ret,item)=> (...args)=>ret(item(...args)))
}
function bindActionCreator(creator, dispatch){
    return (...args) => dispatch(creator(...args))
}
export function bindActionCreators(creators,dispatch){
    return Object.keys(creators).reduce((ret,item)=>{
        ret[item] = bindActionCreator(creators[item],dispatch)
        return ret
    },{})
}