源码解析

前言

• 1.Vue.use通过install混入vue-router上 beforeCreate 代码，定义了_route变量，指向了当前路由组件实例
• 2.路由实例化内部会让window设置监听事件监听路由变化修改_route参数，并且安装<router-link> 和 <router-view> ，然后将路由相关组件传入new Vue实例中
• 3.执行vue实例会执行之前混入beforeCreate相关逻辑，router-view会随着_route参数的修改触发组件更新

Vue Router 官网 (opens new window)

1.项目代码

• mian.js

import Vue from "vue"
import App from "./App"
import router from "./router"

new Vue({
  el: "#app",
  router,
  render: (h) => h(App),
})

• import router from "./router"

import Vue from "vue"
import Router from "vue-router"

Vue.use(Router)
let router = new Router({
  base: "/abstract-vue/",
  mode: "history",
  routes: [
    {
      path: "/",
      name: "login",
      component: () => import("@/views/Login"),
    },
  ],
})

export default router

2.首次加载

2.1 Vue.use

• /src/vue-router/src/install.js

export function install (Vue) {
  if (install.installed && _Vue === Vue) return
  install.installed = true

  _Vue = Vue

  const isDef = v => v !== undefined

  const registerInstance = (vm, callVal) => {
    let i = vm.$options._parentVnode
    if (isDef(i) && isDef(i = i.data) && isDef(i = i.registerRouteInstance)) {
      i(vm, callVal)
    }
  }

  Vue.mixin({
    beforeCreate () {
      if (isDef(this.$options.router)) {
        this._routerRoot = this
        this._router = this.$options.router
        this._router.init(this)
        Vue.util.defineReactive(this, '_route', this._router.history.current)
      } else {
        this._routerRoot = (this.$parent && this.$parent._routerRoot) || this
      }
      registerInstance(this, this)
    },
    destroyed () {
      registerInstance(this)
    }
  })

  Object.defineProperty(Vue.prototype, '$router', {
    get () { return this._routerRoot._router }
  })

  Object.defineProperty(Vue.prototype, '$route', {
    get () { return this._routerRoot._route }
  })

  Vue.component('RouterView', View)
  Vue.component('RouterLink', Link)

  const strats = Vue.config.optionMergeStrategies
  // use the same hook merging strategy for route hooks
  strats.beforeRouteEnter = strats.beforeRouteLeave = strats.beforeRouteUpdate = strats.created
}

install执行时首先会调用Vue.mixin将beforeCreate和destroyed钩子函数注入到每一个组件中

在 Vue 原型上定义了 $router 和 $route 2 个属性的 get ⽅法

⼜通过 Vue.component ⽅法定义了全局的 <router-link> 和 <router-view> 2 个组件

2.2 new Router

• /src/vue-router/src/router.js

export default class VueRouter {
  static install: () => void
  static version: string
  static isNavigationFailure: Function
  static NavigationFailureType: any
  static START_LOCATION: Route

  app: any
  apps: Array<any>
  ready: boolean
  readyCbs: Array<Function>
  options: RouterOptions
  mode: string
  history: HashHistory | HTML5History | AbstractHistory
  matcher: Matcher
  fallback: boolean
  beforeHooks: Array<?NavigationGuard>
  resolveHooks: Array<?NavigationGuard>
  afterHooks: Array<?AfterNavigationHook>

  constructor (options: RouterOptions = {}) {
    if (process.env.NODE_ENV !== 'production') {
      warn(this instanceof VueRouter, `Router must be called with the new operator.`)
    }
    this.app = null
    this.apps = []
    this.options = options
    this.beforeHooks = []
    this.resolveHooks = []
    this.afterHooks = []
    this.matcher = createMatcher(options.routes || [], this)

    let mode = options.mode || 'hash'
    this.fallback =
      mode === 'history' && !supportsPushState && options.fallback !== false
    if (this.fallback) {
      mode = 'hash'
    }
    if (!inBrowser) {
      mode = 'abstract'
    }
    this.mode = mode

    switch (mode) {
      case 'history':
        this.history = new HTML5History(this, options.base)
        break
      case 'hash':
        this.history = new HashHistory(this, options.base, this.fallback)
        break
      case 'abstract':
        this.history = new AbstractHistory(this, options.base)
        break
      default:
        if (process.env.NODE_ENV !== 'production') {
          assert(false, `invalid mode: ${mode}`)
        }
    }
  }

  match (raw: RawLocation, current?: Route, redirectedFrom?: Location): Route {
    return this.matcher.match(raw, current, redirectedFrom)
  }

  get currentRoute (): ?Route {
    return this.history && this.history.current
  }

  init (app: any /* Vue component instance */) {
    process.env.NODE_ENV !== 'production' &&
      assert(
        install.installed,
        `not installed. Make sure to call \`Vue.use(VueRouter)\` ` +
          `before creating root instance.`
      )

    this.apps.push(app)

    // set up app destroyed handler
    // https://github.com/vuejs/vue-router/issues/2639
    app.$once('hook:destroyed', () => {
      // clean out app from this.apps array once destroyed
      const index = this.apps.indexOf(app)
      if (index > -1) this.apps.splice(index, 1)
      // ensure we still have a main app or null if no apps
      // we do not release the router so it can be reused
      if (this.app === app) this.app = this.apps[0] || null

      if (!this.app) this.history.teardown()
    })

    // main app previously initialized
    // return as we don't need to set up new history listener
    if (this.app) {
      return
    }

    this.app = app

    const history = this.history

    if (history instanceof HTML5History || history instanceof HashHistory) {
      const handleInitialScroll = routeOrError => {
        const from = history.current
        const expectScroll = this.options.scrollBehavior
        const supportsScroll = supportsPushState && expectScroll

        if (supportsScroll && 'fullPath' in routeOrError) {
          handleScroll(this, routeOrError, from, false)
        }
      }
      const setupListeners = routeOrError => {
        history.setupListeners()
        handleInitialScroll(routeOrError)
      }
      history.transitionTo(
        history.getCurrentLocation(),
        setupListeners,
        setupListeners
      )
    }

    history.listen(route => {
      this.apps.forEach(app => {
        app._route = route
      })
    })
  }

  beforeEach (fn: Function): Function {
    return registerHook(this.beforeHooks, fn)
  }

  beforeResolve (fn: Function): Function {
    return registerHook(this.resolveHooks, fn)
  }

  afterEach (fn: Function): Function {
    return registerHook(this.afterHooks, fn)
  }

  onReady (cb: Function, errorCb?: Function) {
    this.history.onReady(cb, errorCb)
  }

  onError (errorCb: Function) {
    this.history.onError(errorCb)
  }

  push (location: RawLocation, onComplete?: Function, onAbort?: Function) {
    // $flow-disable-line
    if (!onComplete && !onAbort && typeof Promise !== 'undefined') {
      return new Promise((resolve, reject) => {
        this.history.push(location, resolve, reject)
      })
    } else {
      this.history.push(location, onComplete, onAbort)
    }
  }

  replace (location: RawLocation, onComplete?: Function, onAbort?: Function) {
    // $flow-disable-line
    if (!onComplete && !onAbort && typeof Promise !== 'undefined') {
      return new Promise((resolve, reject) => {
        this.history.replace(location, resolve, reject)
      })
    } else {
      this.history.replace(location, onComplete, onAbort)
    }
  }

  go (n: number) {
    this.history.go(n)
  }

  back () {
    this.go(-1)
  }

  forward () {
    this.go(1)
  }

  getMatchedComponents (to?: RawLocation | Route): Array<any> {
    const route: any = to
      ? to.matched
        ? to
        : this.resolve(to).route
      : this.currentRoute
    if (!route) {
      return []
    }
    return [].concat.apply(
      [],
      route.matched.map(m => {
        return Object.keys(m.components).map(key => {
          return m.components[key]
        })
      })
    )
  }

  resolve (
    to: RawLocation,
    current?: Route,
    append?: boolean
  ): {
    location: Location,
    route: Route,
    href: string,
    // for backwards compat
    normalizedTo: Location,
    resolved: Route
  } {
    current = current || this.history.current
    const location = normalizeLocation(to, current, append, this)
    const route = this.match(location, current)
    const fullPath = route.redirectedFrom || route.fullPath
    const base = this.history.base
    const href = createHref(base, fullPath, this.mode)
    return {
      location,
      route,
      href,
      // for backwards compat
      normalizedTo: location,
      resolved: route
    }
  }

  getRoutes () {
    return this.matcher.getRoutes()
  }

  addRoute (parentOrRoute: string | RouteConfig, route?: RouteConfig) {
    this.matcher.addRoute(parentOrRoute, route)
    if (this.history.current !== START) {
      this.history.transitionTo(this.history.getCurrentLocation())
    }
  }

  addRoutes (routes: Array<RouteConfig>) {
    if (process.env.NODE_ENV !== 'production') {
      warn(false, 'router.addRoutes() is deprecated and has been removed in Vue Router 4. Use router.addRoute() instead.')
    }
    this.matcher.addRoutes(routes)
    if (this.history.current !== START) {
      this.history.transitionTo(this.history.getCurrentLocation())
    }
  }
}

2.3 new Vue

new Vue({
  ...
  router,
  ...
})

• 项目通过此变量Vue与vue-router结合在一起（名称固定写死）

this._router = this.$options.router

2.4 首次渲染

3.跳转进入

4.跳转离开