Vue源码解析(一)
前言:接触vue已经有一段时间了,前面也写了几篇关于vue全家桶的内容,感兴趣的小伙伴可以去看看,刚接触的时候就想去膜拜一下源码~可每次鼓起勇气去看vue源码的时候,当看到几万行代码的时候就直接望而却步了,小伙伴是不是也跟我当初一样呢? 下面分享一下我看vue源码的一些感触,然后记录一下我对源码的理解,欢迎指正,纯属个人笔记,大牛勿喷!
我们直接上一张vue官网的vue的生命周期图:
我们跟着源码结合demo把张图全部跑一遍~~
我们以一个webpack+vue单页面引用为demo
首先我们看一下vue源码文件:
我们首先从我们项目的main.js文件开始:
// The Vue build version to load with the `import` command
// (runtime-only or standalone) has been set in webpack.base.conf with an alias.
import Vue from 'vue'
import App from './App'
import router from './router'
import store from './store'
import LazyImage from './lazy'
import {sync} from 'vuex-router-sync'
Vue.config.productionTip = false
Vue.use(LazyImage)
sync(store,router)
/* eslint-disable no-new */
new Vue({
el: '#app',
router,
store,
ddd: {name: 'yasin'},
render(h) {
return h(App)
}
})
我们已经默默的开始的我们的旅程,目前已经到达了生命周期的(new Vue())
我们点开vue的源码(/node_modules/vue/src/core),找到构造函数:
import Vue from './instance/index'
import { initGlobalAPI } from './global-api/index'
import { isServerRendering } from 'core/util/env'
import { FunctionalRenderContext } from 'core/vdom/create-functional-component'
initGlobalAPI(Vue)
Object.defineProperty(Vue.prototype, '$isServer', {
get: isServerRendering
})
Object.defineProperty(Vue.prototype, '$ssrContext', {
get () {
/* istanbul ignore next */
return this.$vnode && this.$vnode.ssrContext
}
})
// expose FunctionalRenderContext for ssr runtime helper installation
Object.defineProperty(Vue, 'FunctionalRenderContext', {
value: FunctionalRenderContext
})
Vue.version = '__VERSION__'
export default Vue
入口文件中定义了一些服务端渲染的东西,我们不关心,继续往下走
/node_modules/vue/src/core/instance:
import { initMixin } from './init'
import { stateMixin } from './state'
import { renderMixin } from './render'
import { eventsMixin } from './events'
import { lifecycleMixin } from './lifecycle'
import { warn } from '../util/index'
function Vue (options) {
if (process.env.NODE_ENV !== 'production' &&
!(this instanceof Vue)
) {
warn('Vue is a constructor and should be called with the `new` keyword')
}
this._init(options)
}
initMixin(Vue)
stateMixin(Vue)
eventsMixin(Vue)
lifecycleMixin(Vue)
renderMixin(Vue)
export default Vue
好啦~ 整个vue的构造函数中就只调用了一个init方法(我们已经来到了生命周期图的init函数了):
init方法哪里来的呢? 我们可以下面调用了:
initMixin(Vue)
/node_modules/vue/src/core/instance/init.js
export function initMixin (Vue: Class) {
Vue.prototype._init = function (options?: Object) {
const vm: Component = this
// a uid
vm._uid = uid++
let startTag, endTag
/* istanbul ignore if */
if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
startTag = `vue-perf-start:${vm._uid}`
endTag = `vue-perf-end:${vm._uid}`
mark(startTag)
}
// a flag to avoid this being observed
vm._isVue = true
// merge options
if (options && options._isComponent) {
// optimize internal component instantiation
// since dynamic options merging is pretty slow, and none of the
// internal component options needs special treatment.
initInternalComponent(vm, options)
} else {
vm.$options = mergeOptions(
resolveConstructorOptions(vm.constructor),
options || {},
vm
)
}
/* istanbul ignore else */
if (process.env.NODE_ENV !== 'production') {
initProxy(vm)
} else {
vm._renderProxy = vm
}
// expose real self
vm._self = vm
initLifecycle(vm)
initEvents(vm)
initRender(vm)
callHook(vm, 'beforeCreate')
initInjections(vm) // resolve injections before data/props
initState(vm)
initProvide(vm) // resolve provide after data/props
callHook(vm, 'created')
/* istanbul ignore if */
if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
vm._name = formatComponentName(vm, false)
mark(endTag)
measure(`vue ${vm._name} init`, startTag, endTag)
}
if (vm.$options.el) {
vm.$mount(vm.$options.el)
}
}
}
代码已经有点多了,问题不大~ 我们找重点,我们再看一下生命周期图,看一下我们接下来走哪一步了:
可以看到,我们接下来要走init方法中的events跟lifecyle,字面意思就可以知道是注册“事件”跟“生命周期”的意思:
我们在init方法中找到对应的代码:
Vue.prototype._init = function (options?: Object) {
....
// expose real self
vm._self = vm
initLifecycle(vm)
initEvents(vm)
initRender(vm)
callHook(vm, 'beforeCreate')
....
}
我们首先点开initLifecycle方法:
/node_modules/vue/src/core/instance/lifecycle.js
export function initLifecycle (vm: Component) {
const options = vm.$options
// locate first non-abstract parent
let parent = options.parent
if (parent && !options.abstract) {
while (parent.$options.abstract && parent.$parent) {
parent = parent.$parent
}
parent.$children.push(vm)
}
vm.$parent = parent
vm.$root = parent ? parent.$root : vm
vm.$children = []
vm.$refs = {}
vm._watcher = null
vm._inactive = null
vm._directInactive = false
vm._isMounted = false
vm._isDestroyed = false
vm._isBeingDestroyed = false
}
很简单,就是初始化一些生命周期的变量(未渲染、未销毁等等)
我们接下来看一下init方法中的Events(initEvents):
export function initEvents (vm: Component) {
vm._events = Object.create(null)
vm._hasHookEvent = false
// init parent attached events
const listeners = vm.$options._parentListeners
if (listeners) {
updateComponentListeners(vm, listeners)
}
}
events是啥呢? 就是我们执行vm. o n c e 、 v m . once、vm. once、vm.on、vm.$emit方法发送的一些事件,分为注册事件跟触发事件(观察者模式)
好啦,我们已经把init的events跟lifecycle看完了,在继续往下之前我们再来看一下入口文件的这些方法:
node_modules/vue/src/core/instance/index.js
initMixin(Vue)
stateMixin(Vue)
eventsMixin(Vue)
lifecycleMixin(Vue)
renderMixin(Vue)
export default Vue
initMixin方法我们上面已经看过了
我们看一下 stateMixin方法:
export function stateMixin (Vue: Class) {
// flow somehow has problems with directly declared definition object
// when using Object.defineProperty, so we have to procedurally build up
// the object here.
const dataDef = {}
dataDef.get = function () { return this._data }
const propsDef = {}
propsDef.get = function () { return this._props }
if (process.env.NODE_ENV !== 'production') {
dataDef.set = function (newData: Object) {
warn(
'Avoid replacing instance root $data. ' +
'Use nested data properties instead.',
this
)
}
propsDef.set = function () {
warn(`$props is readonly.`, this)
}
}
Object.defineProperty(Vue.prototype, '$data', dataDef)
Object.defineProperty(Vue.prototype, '$props', propsDef)
Vue.prototype.$set = set
Vue.prototype.$delete = del
Vue.prototype.$watch = function (
expOrFn: string | Function,
cb: any,
options?: Object
): Function {
const vm: Component = this
if (isPlainObject(cb)) {
return createWatcher(vm, expOrFn, cb, options)
}
options = options || {}
options.user = true
const watcher = new Watcher(vm, expOrFn, cb, options)
if (options.immediate) {
cb.call(vm, watcher.value)
}
return function unwatchFn () {
watcher.teardown()
}
}
}
我们在vue项目中代码可能会用到 Vue.prototype. s e t 、 V u e . p r o t o t y p e . set、 Vue.prototype. set、Vue.prototype.delete、 Vue.prototype. w a t c h 方 法 , 我 就 简 单 的 解 释 一 下 V u e . p r o t o t y p e . watch 方法,我就简单的解释一下Vue.prototype. watch方法,我就简单的解释一下Vue.prototype.set的工作原理,其他两个方法小伙伴自己去研究哦~
为什么需要用到vm.$set方法呢?
小伙伴可以看官网解释:
https://cn.vuejs.org/v2/guide/reactivity.html
Vue 不允许在已经创建的实例上动态添加新的根级响应式属性 (root-level reactive property)。然而它可以使用 Vue.set(object, key, value) 方法将响应属性添加到嵌套的对象上.
有点抽象哦,比如你在data中定义了一个user对象,然后你想给user对象添加一个name属性,你直接this.name=xxx是没有响应式的,你需要执行:
vm.$set(this.user,'name','xxxx')
这样你的name属性就具有响应式了,好啦~ 我们继续看源码:
Vue.prototype.$set = set
export function set (target: Array | Object, key: any, val: any): any {
if (process.env.NODE_ENV !== 'production' &&
(isUndef(target) || isPrimitive(target))
) {
warn(`Cannot set reactive property on undefined, null, or primitive value: ${(target: any)}`)
}
if (Array.isArray(target) && isValidArrayIndex(key)) {
target.length = Math.max(target.length, key)
target.splice(key, 1, val)
return val
}
if (key in target && !(key in Object.prototype)) {
target[key] = val
return val
}
const ob = (target: any).__ob__
if (target._isVue || (ob && ob.vmCount)) {
process.env.NODE_ENV !== 'production' && warn(
'Avoid adding reactive properties to a Vue instance or its root $data ' +
'at runtime - declare it upfront in the data option.'
)
return val
}
if (!ob) {
target[key] = val
return val
}
defineReactive(ob.value, key, val)
ob.dep.notify()
return val
}
我们看最关键的一行:
defineReactive(ob.value, key, val)
export function defineReactive (
obj: Object,
key: string,
val: any,
customSetter?: ?Function,
shallow?: boolean
) {
const dep = new Dep()
const property = Object.getOwnPropertyDescriptor(obj, key)
if (property && property.configurable === false) {
return
}
// cater for pre-defined getter/setters
const getter = property && property.get
if (!getter && arguments.length === 2) {
val = obj[key]
}
const setter = property && property.set
let childOb = !shallow && observe(val)
Object.defineProperty(obj, key, {
enumerable: true,
configurable: true,
get: function reactiveGetter () {
const value = getter ? getter.call(obj) : val
if (Dep.target) {
dep.depend()
if (childOb) {
childOb.dep.depend()
if (Array.isArray(value)) {
dependArray(value)
}
}
}
return value
},
set: function reactiveSetter (newVal) {
const value = getter ? getter.call(obj) : val
/* eslint-disable no-self-compare */
if (newVal === value || (newVal !== newVal && value !== value)) {
return
}
/* eslint-enable no-self-compare */
if (process.env.NODE_ENV !== 'production' && customSetter) {
customSetter()
}
if (setter) {
setter.call(obj, newVal)
} else {
val = newVal
}
childOb = !shallow && observe(newVal)
dep.notify()
}
})
}
可以看到,最后执行了 Object.defineProperty方法,而 Object.defineProperty方法正好也是vue的mvvm机制的工作原理
继续回头看一下入口文件方法:
initMixin(Vue)
stateMixin(Vue)
eventsMixin(Vue)
lifecycleMixin(Vue)
renderMixin(Vue)
export default Vue
我们已经继续lifecycleMixin
export function lifecycleMixin (Vue: Class) {
Vue.prototype._update = function (vnode: VNode, hydrating?: boolean) {
const vm: Component = this
if (vm._isMounted) {
callHook(vm, 'beforeUpdate')
}
const prevEl = vm.$el
const prevVnode = vm._vnode
const prevActiveInstance = activeInstance
activeInstance = vm
vm._vnode = vnode
// Vue.prototype.__patch__ is injected in entry points
// based on the rendering backend used.
if (!prevVnode) {
// initial render
vm.$el = vm.__patch__(
vm.$el, vnode, hydrating, false /* removeOnly */,
vm.$options._parentElm,
vm.$options._refElm
)
// no need for the ref nodes after initial patch
// this prevents keeping a detached DOM tree in memory (#5851)
vm.$options._parentElm = vm.$options._refElm = null
} else {
// updates
vm.$el = vm.__patch__(prevVnode, vnode)
}
activeInstance = prevActiveInstance
// update __vue__ reference
if (prevEl) {
prevEl.__vue__ = null
}
if (vm.$el) {
vm.$el.__vue__ = vm
}
// if parent is an HOC, update its $el as well
if (vm.$vnode && vm.$parent && vm.$vnode === vm.$parent._vnode) {
vm.$parent.$el = vm.$el
}
// updated hook is called by the scheduler to ensure that children are
// updated in a parent's updated hook.
}
Vue.prototype.$forceUpdate = function () {
const vm: Component = this
if (vm._watcher) {
vm._watcher.update()
}
}
Vue.prototype.$destroy = function () {
const vm: Component = this
if (vm._isBeingDestroyed) {
return
}
callHook(vm, 'beforeDestroy')
vm._isBeingDestroyed = true
// remove self from parent
const parent = vm.$parent
if (parent && !parent._isBeingDestroyed && !vm.$options.abstract) {
remove(parent.$children, vm)
}
// teardown watchers
if (vm._watcher) {
vm._watcher.teardown()
}
let i = vm._watchers.length
while (i--) {
vm._watchers[i].teardown()
}
// remove reference from data ob
// frozen object may not have observer.
if (vm._data.__ob__) {
vm._data.__ob__.vmCount--
}
// call the last hook...
vm._isDestroyed = true
// invoke destroy hooks on current rendered tree
vm.__patch__(vm._vnode, null)
// fire destroyed hook
callHook(vm, 'destroyed')
// turn off all instance listeners.
vm.$off()
// remove __vue__ reference
if (vm.$el) {
vm.$el.__vue__ = null
}
// release circular reference (#6759)
if (vm.$vnode) {
vm.$vnode.parent = null
}
}
}
又是一长串代码,还是一句话:“不要慌,问题不大!! 我们找关键点”
主要就是注册了几个方法:
Vue.prototype._update :vnode对象更新时候触发
Vue.prototype. f o r c e U p d a t e : 强 制 更 新 v n o d e 对 象 V u e . p r o t o t y p e . forceUpdate :强制更新vnode对象 Vue.prototype. forceUpdate:强制更新vnode对象Vue.prototype.destroy :销毁当前vnode对象
官网解释说是:“可以说这三个方法一般是用不到的,除非你代码出问题了~”
我重点说一下 f o r c e U p d a t e 方 法 , 还 是 跟 上 面 说 的 forceUpdate方法,还是跟上面说的 forceUpdate方法,还是跟上面说的set方法一样,当你动态给一个data对象添加一个属性的时候,如果没有用 s e t 方 法 的 话 , 属 性 是 不 具 有 响 应 式 效 果 , 但 是 又 要 刷 新 页 面 怎 么 办 呢 ? 这 个 时 候 你 可 以 使 用 set方法的话,属性是不具有响应式效果,但是又要刷新页面怎么办呢? 这个时候你可以使用 set方法的话,属性是不具有响应式效果,但是又要刷新页面怎么办呢?这个时候你可以使用forceUpdate方法.
我说是这么说哈,小伙伴项目中可别这么干,因为当你用$forceUpdate方法解决问题的时候,90%是你程序出错了.
我们继续看入口文件:
initMixin(Vue)
stateMixin(Vue)
eventsMixin(Vue)
lifecycleMixin(Vue)
renderMixin(Vue)
export default Vue
还差最后一个renderMixin(Vue)方法:
export function renderMixin (Vue: Class) {
// install runtime convenience helpers
installRenderHelpers(Vue.prototype)
Vue.prototype.$nextTick = function (fn: Function) {
return nextTick(fn, this)
}
Vue.prototype._render = function (): VNode {
const vm: Component = this
const { render, _parentVnode } = vm.$options
// reset _rendered flag on slots for duplicate slot check
if (process.env.NODE_ENV !== 'production') {
for (const key in vm.$slots) {
// $flow-disable-line
vm.$slots[key]._rendered = false
}
}
if (_parentVnode) {
vm.$scopedSlots = _parentVnode.data.scopedSlots || emptyObject
}
// set parent vnode. this allows render functions to have access
// to the data on the placeholder node.
vm.$vnode = _parentVnode
// render self
let vnode
try {
vnode = render.call(vm._renderProxy, vm.$createElement)
} catch (e) {
handleError(e, vm, `render`)
// return error render result,
// or previous vnode to prevent render error causing blank component
/* istanbul ignore else */
if (process.env.NODE_ENV !== 'production') {
if (vm.$options.renderError) {
try {
vnode = vm.$options.renderError.call(vm._renderProxy, vm.$createElement, e)
} catch (e) {
handleError(e, vm, `renderError`)
vnode = vm._vnode
}
} else {
vnode = vm._vnode
}
} else {
vnode = vm._vnode
}
}
// return empty vnode in case the render function errored out
if (!(vnode instanceof VNode)) {
if (process.env.NODE_ENV !== 'production' && Array.isArray(vnode)) {
warn(
'Multiple root nodes returned from render function. Render function ' +
'should return a single root node.',
vm
)
}
vnode = createEmptyVNode()
}
// set parent
vnode.parent = _parentVnode
return vnode
}
创建了两个方法:
Vue.prototype.$nextTick
Vue.prototype._render
_render方法先搁一会,后面会详细介绍,我们先看一下nextTick方法,当然,官网也有解释:
例如，当你设置 vm.someData = ‘new value’ ，该组件不会立即重新渲染。当刷新队列时，组件会在事件循环队列清空时的下一个“tick”更新。多数情况我们不需要关心这个过程，但是如果你想在 DOM 状态更新后做点什么，这就可能会有些棘手。虽然 Vue.js 通常鼓励开发人员沿着“数据驱动”的方式思考，避免直接接触 DOM，但是有时我们确实要这么做。为了在数据变化之后等待 Vue 完成更新 DOM ，可以在数据变化之后立即使用 Vue.nextTick(callback) 。
我简单说一下原理: 当你执行vm.someData = ‘new value’—>触发vm的update方法更新vnode—>vnode判断平台(web、week)做dom操作–>更新完dom后回调nextTick方法
好啦,入口文件的几个方法我们都研究完了,我们再回顾一下生命周期图:
我们已经走到了第三步了(init方法的injections跟reactivity)
我们找到init方法的这段代码:
Vue.prototype._init = function (options?: Object) {
....
initInjections(vm) // resolve injections before data/props
initState(vm)
initProvide(vm) // resolve provide after data/props
....
}
我们首先看一下initInjections方法:
export function initInjections (vm: Component) {
const result = resolveInject(vm.$options.inject, vm)
if (result) {
toggleObserving(false)
Object.keys(result).forEach(key => {
/* istanbul ignore else */
if (process.env.NODE_ENV !== 'production') {
defineReactive(vm, key, result[key], () => {
warn(
`Avoid mutating an injected value directly since the changes will be ` +
`overwritten whenever the provided component re-renders. ` +
`injection being mutated: "${key}"`,
vm
)
})
} else {
defineReactive(vm, key, result[key])
}
})
toggleObserving(true)
}
}
看代码有点懵逼,什么意思呢?比如在父类或者超类组件中定义了一些基础数据,子类组件需要拿到这些基础数据,我们就可以用inject,inject中包含了initInjections跟initProvide.
怎么用呢?
比如我们的组件render1.vue中定义了一个叫title的字段:
然后我们可以在render2中拿到我们的title字段:
render2.vue
render2.vue中只需要在当前vm的options中提供inject对象然后需要标明需要注入的属性来自哪:
inject: {
name: { //需要注入的key
from: 'title' //来自父组件的什么字段比如:“title”
}
}
我们就可以在当前的render2.vue中使用this.name访问render1.vue中的title字段了,小伙伴可以自己尝试一下哦~
好啦,我们继续我们的生命周期解析,当解析完了init方法的events,我们还差一个reactivity:
Vue.prototype._init = function (options?: Object) {
....
callHook(vm, 'beforeCreate')
initInjections(vm) // resolve injections before data/props
initState(vm)
initProvide(vm) // resolve provide after data/props
callHook(vm, 'created')
....
我们直接点开initState方法:
export function initState (vm: Component) {
vm._watchers = []
const opts = vm.$options
if (opts.props) initProps(vm, opts.props)
if (opts.methods) initMethods(vm, opts.methods)
if (opts.data) {
initData(vm)
} else {
observe(vm._data = {}, true /* asRootData */)
}
if (opts.computed) initComputed(vm, opts.computed)
if (opts.watch && opts.watch !== nativeWatch) {
initWatch(vm, opts.watch)
}
}
initState的目的就是初始化一些响应式操作,具体有:data属性、props属性、computed属性、watch属性. 想必小伙伴用的最多的就是这几个属性了,我们改变一个组件的props、data、computed、都会触发响应式操作然后更新组件,watch里面的属性如果改变了也会触发watch方法,那么它们的工作原理是是什么呢?
我们首先看props,我们看到这么一行代码:
export function initState (vm: Component) {
vm._watchers = []
const opts = vm.$options
if (opts.props) initProps(vm, opts.props)
....
}
function initProps (vm: Component, propsOptions: Object) {
//获取我们的属性值（也就是我们在组件中传递的属性）
const propsData = vm.$options.propsData || {}
//定义当前vm的_props对象
const props = vm._props = {}
// cache prop keys so that future props updates can iterate using Array
// instead of dynamic object key enumeration.
const keys = vm.$options._propKeys = []
const isRoot = !vm.$parent
// root instance props should be converted
if (!isRoot) {
toggleObserving(false)
}
//遍历我们在组件中定义的props
for (const key in propsOptions) {
keys.push(key)
//验证props
const value = validateProp(key, propsOptions, propsData, vm)
/* istanbul ignore else */
if (process.env.NODE_ENV !== 'production') {
const hyphenatedKey = hyphenate(key)
if (isReservedAttribute(hyphenatedKey) ||
config.isReservedAttr(hyphenatedKey)) {
warn(
`"${hyphenatedKey}" is a reserved attribute and cannot be used as component prop.`,
vm
)
}
//给当前vm的_props对象添加响应式属性（也就是我们传递的属性值）
defineReactive(props, key, value, () => {
if (vm.$parent && !isUpdatingChildComponent) {
warn(
`Avoid mutating a prop directly since the value will be ` +
`overwritten whenever the parent component re-renders. ` +
`Instead, use a data or computed property based on the prop's ` +
`value. Prop being mutated: "${key}"`,
vm
)
}
})
} else {
//给当前vm的_props对象添加响应式属性（也就是我们传递的属性值）
defineReactive(props, key, value)
}
// static props are already proxied on the component's prototype
// during Vue.extend(). We only need to proxy props defined at
// instantiation here.
//把vm中的属性通过代理方式指向_props对象（也就是我们可以在vm中通过this.xxx访问某个属性）
if (!(key in vm)) {
proxy(vm, `_props`, key)
}
}
toggleObserving(true)
}
代码中都有解释,我就不多说了,data跟props的原理差不多,watch跟computed无非就是一些响应的回调触发,我们也不多说了~~
我们已经把vue created之前生命周期源码解析了一遍,再看一眼生命周期图:
callHook(vm, 'created')
...
if (vm.$options.el) {
vm.$mount(vm.$options.el)
}
当我们给vue实例传递了el参数的时候,vue会直接调用mount方法,然后就会走渲染逻辑,当然,如果我们没有el参数的时候,我们可以手动的调用mount方法把vue实例挂载到某个dom元素中,所以接下来我们重点研究一下mount方法.
那么mount方法在哪定义的呢?
我们找到这么一个文件
/vue/src/platforms/web/runtime/index.js
// public mount method
Vue.prototype.$mount = function (
el?: string | Element,
hydrating?: boolean
): Component {
el = el && inBrowser ? query(el) : undefined
return mountComponent(this, el, hydrating)
}
然后在vue/src/platforms/web/entry-runtime-with-compiler.js文件中又再一次对mount方法重定义了:
const mount = Vue.prototype.$mount
Vue.prototype.$mount = function (
el?: string | Element,
hydrating?: boolean
): Component {
el = el && query(el)
/* istanbul ignore if */
if (el === document.body || el === document.documentElement) {
process.env.NODE_ENV !== 'production' && warn(
`Do not mount Vue to or - mount to normal elements instead.`
)
return this
}
const options = this.$options
// resolve template/el and convert to render function
if (!options.render) {
let template = options.template
if (template) {
if (typeof template === 'string') {
if (template.charAt(0) === '#') {
template = idToTemplate(template)
/* istanbul ignore if */
if (process.env.NODE_ENV !== 'production' && !template) {
warn(
`Template element not found or is empty: ${options.template}`,
this
)
}
}
} else if (template.nodeType) {
template = template.innerHTML
} else {
if (process.env.NODE_ENV !== 'production') {
warn('invalid template option:' + template, this)
}
return this
}
} else if (el) {
template = getOuterHTML(el)
}
if (template) {
/* istanbul ignore if */
if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
mark('compile')
}
const { render, staticRenderFns } = compileToFunctions(template, {
shouldDecodeNewlines,
shouldDecodeNewlinesForHref,
delimiters: options.delimiters,
comments: options.comments
}, this)
options.render = render
options.staticRenderFns = staticRenderFns
/* istanbul ignore if */
if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
mark('compile end')
measure(`vue ${this._name} compile`, 'compile', 'compile end')
}
}
}
return mount.call(this, el, hydrating)
}
可以看到,最后执行了mount.call,而这里的mount方法是/vue/src/platforms/web/runtime/index.js文件中定义的,而/vue/src/platforms/web/runtime/index.js文件中的mount方法:
// public mount method
Vue.prototype.$mount = function (
el?: string | Element,
hydrating?: boolean
): Component {
el = el && inBrowser ? query(el) : undefined
return mountComponent(this, el, hydrating)
}
最后执行了mountComponent方法,而mountComponent又是vue/VuexDemo/node_modules/vue/src/core/instance/render.js文件中定义的:
export function renderMixin (Vue: Class) {
// install runtime convenience helpers
installRenderHelpers(Vue.prototype)
Vue.prototype.$nextTick = function (fn: Function) {
return nextTick(fn, this)
}
Vue.prototype._render = function (): VNode {
const vm: Component = this
const { render, _parentVnode } = vm.$options
// reset _rendered flag on slots for duplicate slot check
if (process.env.NODE_ENV !== 'production') {
for (const key in vm.$slots) {
// $flow-disable-line
vm.$slots[key]._rendered = false
}
}
if (_parentVnode) {
vm.$scopedSlots = _parentVnode.data.scopedSlots || emptyObject
}
// set parent vnode. this allows render functions to have access
// to the data on the placeholder node.
vm.$vnode = _parentVnode
// render self
let vnode
try {
vnode = render.call(vm._renderProxy, vm.$createElement)
} catch (e) {
handleError(e, vm, `render`)
// return error render result,
// or previous vnode to prevent render error causing blank component
/* istanbul ignore else */
if (process.env.NODE_ENV !== 'production') {
if (vm.$options.renderError) {
try {
vnode = vm.$options.renderError.call(vm._renderProxy, vm.$createElement, e)
} catch (e) {
handleError(e, vm, `renderError`)
vnode = vm._vnode
}
} else {
vnode = vm._vnode
}
} else {
vnode = vm._vnode
}
}
// return empty vnode in case the render function errored out
if (!(vnode instanceof VNode)) {
if (process.env.NODE_ENV !== 'production' && Array.isArray(vnode)) {
warn(
'Multiple root nodes returned from render function. Render function ' +
'should return a single root node.',
vm
)
}
vnode = createEmptyVNode()
}
// set parent
vnode.parent = _parentVnode
return vnode
}
}
好吧,小伙伴是不是有点绕了呢? 还是那句话:“别慌,问题不大!! 我们看重点~~”
首先当我们直接调用vm的mount方法的时候会触发最后一个定义mount方法的地方,也就是上面的/vue/src/platforms/web/entry-runtime-with-compiler.js:
const mount = Vue.prototype.$mount
Vue.prototype.$mount = function (
el?: string | Element,
hydrating?: boolean
): Component {
//在vm中传递的el属性
el = el && query(el)
/* istanbul ignore if */
if (el === document.body || el === document.documentElement) {
process.env.NODE_ENV !== 'production' && warn(
`Do not mount Vue to or - mount to normal elements instead.`
)
return this
}
const options = this.$options
// 如果在options中没有传递render方法
if (!options.render) {
let template = options.template
//如果有template属性，就把template编译完毕后传递给render方法
if (template) {
if (typeof template === 'string') {
if (template.charAt(0) === '#') {
template = idToTemplate(template)
/* istanbul ignore if */
if (process.env.NODE_ENV !== 'production' && !template) {
warn(
`Template element not found or is empty: ${options.template}`,
this
)
}
}
} else if (template.nodeType) {
template = template.innerHTML
} else {
if (process.env.NODE_ENV !== 'production') {
warn('invalid template option:' + template, this)
}
return this
}
} else if (el) {
//如果没有template属性但是有el属性的时候，把el的outerHtml当成template传递给render对象
template = getOuterHTML(el)
}
if (template) {
/* istanbul ignore if */
if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
mark('compile')
}
const { render, staticRenderFns } = compileToFunctions(template, {
shouldDecodeNewlines,
shouldDecodeNewlinesForHref,
delimiters: options.delimiters,
comments: options.comments
}, this)
options.render = render
options.staticRenderFns = staticRenderFns
/* istanbul ignore if */
if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
mark('compile end')
measure(`vue ${this._name} compile`, 'compile', 'compile end')
}
}
}
return mount.call(this, el, hydrating)
}
最后走到了mountComponent方法(很关键):
vue/src/core/instance/lifecycle.js
export function mountComponent (
vm: Component,
el: ?Element,
hydrating?: boolean
): Component {
vm.$el = el
if (!vm.$options.render) {
vm.$options.render = createEmptyVNode
if (process.env.NODE_ENV !== 'production') {
/* istanbul ignore if */
if ((vm.$options.template && vm.$options.template.charAt(0) !== '#') ||
vm.$options.el || el) {
warn(
'You are using the runtime-only build of Vue where the template ' +
'compiler is not available. Either pre-compile the templates into ' +
'render functions, or use the compiler-included build.',
vm
)
} else {
warn(
'Failed to mount component: template or render function not defined.',
vm
)
}
}
}
callHook(vm, 'beforeMount')
let updateComponent
/* istanbul ignore if */
if (process.env.NODE_ENV !== 'production' && config.performance && mark) {
updateComponent = () => {
const name = vm._name
const id = vm._uid
const startTag = `vue-perf-start:${id}`
const endTag = `vue-perf-end:${id}`
mark(startTag)
const vnode = vm._render()
mark(endTag)
measure(`vue ${name} render`, startTag, endTag)
mark(startTag)
vm._update(vnode, hydrating)
mark(endTag)
measure(`vue ${name} patch`, startTag, endTag)
}
} else {
updateComponent = () => {
vm._update(vm._render(), hydrating)
}
}
// we set this to vm._watcher inside the watcher's constructor
// since the watcher's initial patch may call $forceUpdate (e.g. inside child
// component's mounted hook), which relies on vm._watcher being already defined
new Watcher(vm, updateComponent, noop, null, true /* isRenderWatcher */)
hydrating = false
// manually mounted instance, call mounted on self
// mounted is called for render-created child components in its inserted hook
if (vm.$vnode == null) {
vm._isMounted = true
callHook(vm, 'mounted')
}
return vm
}
可以看到,mountComponent方法创建了Watcher对象,Watcher是干什么的呢?Watcher就是监听响应式数据的变换,然后执行updateComponent方法,最后执行update方法:
Vue.prototype._update = function (vnode: VNode, hydrating?: boolean) {
const vm: Component = this
if (vm._isMounted) {
callHook(vm, 'beforeUpdate')
}
const prevEl = vm.$el
const prevVnode = vm._vnode
const prevActiveInstance = activeInstance
activeInstance = vm
vm._vnode = vnode
// Vue.prototype.__patch__ is injected in entry points
// based on the rendering backend used.
if (!prevVnode) {
// initial render
vm.$el = vm.__patch__(
vm.$el, vnode, hydrating, false /* removeOnly */,
vm.$options._parentElm,
vm.$options._refElm
)
// no need for the ref nodes after initial patch
// this prevents keeping a detached DOM tree in memory (#5851)
vm.$options._parentElm = vm.$options._refElm = null
} else {
// updates
vm.$el = vm.__patch__(prevVnode, vnode)
}
activeInstance = prevActiveInstance
// update __vue__ reference
if (prevEl) {
prevEl.__vue__ = null
}
if (vm.$el) {
vm.$el.__vue__ = vm
}
// if parent is an HOC, update its $el as well
if (vm.$vnode && vm.$parent && vm.$vnode === vm.$parent._vnode) {
vm.$parent.$el = vm.$el
}
// updated hook is called by the scheduler to ensure that children are
// updated in a parent's updated hook.
}
然后修改dom元素,最后刷新页面~~
好啦!! 整个vue的生命周期的流程图就大致走了一遍了~~
下一节我们重点说一下render函数跟mount函数.
先到这里啦，欢迎志同道合的小伙伴入群，一起交流一起学习～～ 加油骚年！！
qq群链接：
