Part01 What's the problem
这段代码意图是把router传递props的路由信息再传递给redux。有这么几个问题：
- 如果靠组件生命周期转发 每个路由下面的顶级组件都要调这样一个action
- 并且，如果路由有参数改变(很多时候页面状态的参数会在路由中体现)，这段代码是无法检测的，还需要在componentWillReceiveProps里去处理逻辑。
- 还有这个setTimeout解决异步问题，极度不优雅。
Can't cooperate
redux 是状态管理的库，router 是(唯一)控制页面跳转的库。两者都很美好，但是不美好的是两者无法协同工作。换句话说，当路由变化以后，store 无法感知到。
redux是想把绝大多数应用程序的状态都保存在单一的store里，而当前的路由状态明显是应用程序状态很重要的一部分，应当是要保存在store中的。
目前是，如果直接使用react router，就意味着所有路由相关的信息脱离了Redux store的控制，假借组件接受router信息转发dispatch的方法属于反模式，违背了redux的设计思想，也给我们应用程序带来了更多的不确定性。
Part02 What do we need
我们需要一个这样的路由系统，他技能利用React Router的声明式特性，又能将路由信息整合进Redux Store中。
react-router-redux
react-router-redux 是 redux 的一个中间件(中间件：JavaScript 代理模式的另一种实践 针对 dispatch 实现了方法的代理，在 dispatch action 的时候增加或者修改) ，主要作用是：
加强了React Router库中history这个实例，以允许将history中接受到的变化反应到state中去。
Part03 How to use
import React from 'react'
import ReactDOM from 'react-dom'
import { createStore, combineReducers } from 'redux'
import { Provider } from 'react-redux'
import { Router, Route, browserHistory } from 'react-router'
import { syncHistoryWithStore, routerReducer } from 'react-router-redux'
import reducers from '<project-path>/reducers'
const store = createStore(
combineReducers({
...reducers,
routing: routerReducer
})
)
const history = syncHistoryWithStore(browserHistory, store)
ReactDOM.render(
<Provider store={store}>
<Router history={history}>
<Route path="/" component={App} />
</Router>
</Provider>,
document.getElementById(‘app')
)使用简单直白的api syncHistoryWithStore来完成redux的绑定工作，我们只需要传入react router中的history（前面提到的）以及redux中的store,就可以获得一个增强后的history对象。
将这个history对象传给react router中的Router组件作为props，就给应用提供了观察路由变化并改变store的能力。
现在，只要您按下浏览器按钮或在应用程序代码中导航，导航就会首先通过Redux存储区传递新位置，然后再传递到React Router以更新组件树。如果您计时旅行，它还会将新状态传递给React Router以再次更新组件树。
如何访问容器组件中的路由器状态？
React Router 通过路径组件的props提供路由信息。这使得从容器组件访问它们变得容易。当使用react-redux对connect()你的组件进行陈述时，你可以从第二个参数mapStateToProps访问路由器的道具：
Part04 Code principle
https://github.com/reactjs/react-router-redux
// index.js
/**
* 作为外部 syncHistoryWithStore
* 绑定store.dispatch方法引起的state中路由状态变更到影响浏览器location变更
* 绑定浏览器location变更触发store.dispatch，更新state中路由状态
* 返回当前的histroy、绑定方法listen（dispatch方法触发时执行，以绑定前的路由状态为参数）、解绑函数unsubscribe
*/
export syncHistoryWithStore from './sync'
/**
* routerReducer监听路由变更子reducer，通过redux的combineReducers复合多个reducer后使用
*/
export { LOCATION_CHANGE, routerReducer } from './reducer'
/**
* 构建actionCreater，作为外部push、replace、go、goBack、goForward方法的接口，通常不直接使用
*/
export {
CALL_HISTORY_METHOD,
push, replace, go, goBack, goForward,
routerActions
} from './actions'
/**
* 构建route中间件，用于分发action，触发路径跳转等事件
*/
export routerMiddleware from './middleware'// sync.js
import { LOCATION_CHANGE } from './reducer'
// 默认用state.routing存取route变更状态数据
const defaultSelectLocationState = state => state.routing
/**
* 作为外部syncHistoryWithStore接口方法
* 绑定store.dispatch方法引起的state中路由状态变更到影响浏览器location变更
* 绑定浏览器location变更触发store.dispatch，更新state中路由状态
* 返回当前的histroy、绑定方法listen（dispatch方法触发时执行，以绑定前的路由状态为参数）、解绑函数unsubscribe
*/
export default function syncHistoryWithStore(history, store, {
// 约定redux.store.state中哪个属性用于存取route变更状态数据
selectLocationState = defaultSelectLocationState,
// store中路由状态变更是否引起浏览器location改变
adjustUrlOnReplay = true
} = {}) {
// Ensure that the reducer is mounted on the store and functioning properly.
// 确保redux.store.state中某个属性绑定了route变更状态
if (typeof selectLocationState(store.getState()) === 'undefined') {
throw new Error(
'Expected the routing state to be available either as `state.routing` ' +
'or as the custom expression you can specify as `selectLocationState` ' +
'in the `syncHistoryWithStore()` options. ' +
'Ensure you have added the `routerReducer` to your store\'s ' +
'reducers via `combineReducers` or whatever method you use to isolate ' +
'your reducers.'
)
}
let initialLocation // 初始化route状态数据
let isTimeTraveling // 浏览器页面location.url改变过程中标识，区别页面链接及react-router-redux变更location两种情况
let unsubscribeFromStore // 移除store.listeners中，因路由状态引起浏览器location变更函数
let unsubscribeFromHistory // 移除location变更引起路由状态更新函数
let currentLocation // 记录上一个当前路由状态数据
// 获取路由事件触发后路由状态，或者useInitialIfEmpty为真值获取初始化route状态，或者undefined
const getLocationInStore = (useInitialIfEmpty) => {
const locationState = selectLocationState(store.getState())
return locationState.locationBeforeTransitions ||
(useInitialIfEmpty ? initialLocation : undefined)
}
// 初始化route状态数据
initialLocation = getLocationInStore()
// If the store is replayed, update the URL in the browser to match.
// adjustUrlOnReplay为真值时，store数据改变事件dispatch发生后，浏览器页面更新location
if (adjustUrlOnReplay) {
// 由store中路由状态改变情况，更新浏览器location
const handleStoreChange = () => {
// 获取路由事件触发后路由状态，或者初始路由状态
const locationInStore = getLocationInStore(true)
if (currentLocation === locationInStore || initialLocation === locationInStore) {
return
}
// 浏览器页面location.url改变过程中标识，区别页面链接及react-router-redux变更location两种情况
isTimeTraveling = true
// 记录上一个当前路由状态数据
currentLocation = locationInStore
// store数据改变后，浏览器页面更新location
history.transitionTo({
...locationInStore,
action: 'PUSH'
})
isTimeTraveling = false
}
// 绑定事件，完成功能为，dispatch方法触发store中路由状态改变时，更新浏览器location
unsubscribeFromStore = store.subscribe(handleStoreChange)
// 初始化设置路由状态时引起页面location改变
handleStoreChange()
}
// 页面链接变更浏览器location，触发store.dispatch变更store中路由状态
const handleLocationChange = (location) => {
// react-router-redux引起浏览器location变更过程中，无效；页面链接变更，有效
if (isTimeTraveling) {
return
}
// Remember where we are
currentLocation = location
// Are we being called for the first time?
if (!initialLocation) {
// Remember as a fallback in case state is reset
initialLocation = location
// Respect persisted location, if any
if (getLocationInStore()) {
return
}
}
// Tell the store to update by dispatching an action
store.dispatch({
type: LOCATION_CHANGE,
payload: location
})
}
// hashHistory、boswerHistory监听浏览器location变更，触发store.dispatch变更store中路由状态
unsubscribeFromHistory = history.listen(handleLocationChange)
// History 3.x doesn't call listen synchronously, so fire the initial location change ourselves
// 初始化更新store中路由状态
if (history.getCurrentLocation) {
handleLocationChange(history.getCurrentLocation())
}
// The enhanced history uses store as source of truth
return {
...history,
// store中dispatch方法触发时，绑定执行函数listener，以绑定前的路由状态为参数
listen(listener) {
// Copy of last location.
// 绑定前的路由状态
let lastPublishedLocation = getLocationInStore(true)
// Keep track of whether we unsubscribed, as Redux store
// only applies changes in subscriptions on next dispatch
let unsubscribed = false // 确保listener在解绑后不执行
const unsubscribeFromStore = store.subscribe(() => {
const currentLocation = getLocationInStore(true)
if (currentLocation === lastPublishedLocation) {
return
}
lastPublishedLocation = currentLocation
if (!unsubscribed) {
listener(lastPublishedLocation)
}
})
// History 2.x listeners expect a synchronous call. Make the first call to the
// listener after subscribing to the store, in case the listener causes a
// location change (e.g. when it redirects)
if (!history.getCurrentLocation) {
listener(lastPublishedLocation)
}
// Let user unsubscribe later
return () => {
unsubscribed = true
unsubscribeFromStore()
}
},
// 解绑函数，包括location到store的handleLocationChange、store到location的handleStoreChange
unsubscribe() {
if (adjustUrlOnReplay) {
unsubscribeFromStore()
}
unsubscribeFromHistory()
}
}
}// reducer.js
/**
* This action type will be dispatched when your history
* receives a location change.
*/
export const LOCATION_CHANGE = '@@router/LOCATION_CHANGE'
const initialState = {
locationBeforeTransitions: null
}
/**
* 监听路由变更子reducer，通过redux的combineReducers复合多个reducer后使用，作为外部routerReducer接口
* 提示redux使用过程中，可通过子组件模块中注入reducer，再使用combineReducers复合多个reducer
* 最后使用replaceReducer方法更新当前store的reducer，意义是构建reducer拆解到各个子模块中
* */
export function routerReducer(state = initialState, { type, payload } = {}) {
if (type === LOCATION_CHANGE) {
return { ...state, locationBeforeTransitions: payload }
}
return state
}// actions.js
export const CALL_HISTORY_METHOD = '@@router/CALL_HISTORY_METHOD'
function updateLocation(method) {
return (...args) => ({
type: CALL_HISTORY_METHOD, // route事件标识，避免和用于定义的action冲突
payload: { method, args } // method系hashHistroy、boswerHistroy对外接口方法名，args为参数
})
}
/**
* 返回actionCreater，作为外部push、replace、go、goBack、goForward方法的接口，通常不直接使用
*/
export const push = updateLocation('push')
export const replace = updateLocation('replace')
export const go = updateLocation('go')
export const goBack = updateLocation('goBack')
export const goForward = updateLocation('goForward')
export const routerActions = { push, replace, go, goBack, goForward }完结
（此文由PPT摘抄完成）PPT链接