Vue数据绑定简析小结

// src/core/instance/index.js
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)
}

// src/core/instance/init.js
Vue.prototype._init = function (options) {
 ...
 // a flag to avoid this being observed
 vm._isVue = true
 // merge options
 // 初始化vm实例的$options
 if (options && options._isComponent) {
  initInternalComponent(vm, options)
 } else {
  vm.$options = mergeOptions(
   resolveConstructorOptions(vm.constructor),
   options || {},
   vm
  )
 }
 ...
 initLifecycle(vm) // 梳理实例的parent、root、children和refs，并初始化一些与生命周期相关的实例属性
 initEvents(vm) // 初始化实例的listeners
 initRender(vm) // 初始化插槽，绑定createElement函数的vm实例
 callHook(vm, 'beforeCreate')
 initInjections(vm) // resolve injections before data/props
 initState(vm)
 initProvide(vm) // resolve provide after data/props
 callHook(vm, 'created')
 
 if (vm.$options.el) {
  vm.$mount(vm.$options.el) // 挂载组件到节点
 }
}

// src/core/instance/state.js
export function initState (vm) {
 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)
 }
}

function initProps (vm, propsOptions) {
 const propsData = vm.$options.propsData || {}
 const props = vm._props = {}
 // cache prop keys so that future props updates can iterate using Array
 // instead of dynamic object key enumeration.
 const keys = vm.$options._propKeys = []
 const isRoot = !vm.$parent
 // root instance props should be converted
 if (!isRoot) {
 toggleObserving(false)
 }
 for (const key in propsOptions) {
 keys.push(key)
 const value = validateProp(key, propsOptions, propsData, vm)
 ...
 defineReactive(props, key, value)
 if (!(key in vm)) {
  proxy(vm, '_props', key)
 }
 }
 toggleObserving(true)
}

export default {
  ...
  props: {
    item: {
      type: Object,
      default: () => ({})
    }
  }
}

const value = validateProp(key, propsOptions, propsData, vm)

if (!(key in vm)) {
 proxy(vm, '_props', key)
}

function proxy (target, sourceKey, key) {
 sharedPropertyDefinition.get = function proxyGetter () {
  return this[sourceKey][key]
 }
 sharedPropertyDefinition.set = function proxySetter (val) {
  this[sourceKey][key] = val
 }
 Object.defineProperty(target, key, sharedPropertyDefinition)
}

// src/core/observer/index.js
export function defineReactive (
 obj,
 key,
 val,
 customSetter,
 shallow
) {
 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
 const setter = property && property.set
 if ((!getter || setter) && arguments.length === 2) {
  val = obj[key]
 }

 let childOb = !shallow && observe(val)
 ...
}

if ((!getter || setter) && arguments.length === 2) {
  val = obj[key]
}

if (getter && !setter) return

let childOb = !shallow && observe(val)

// src/core/observer/index.js
export function observe (value, asRootData) {
 if (!isObject(value) || value instanceof VNode) {
  return
 }
 let ob
 if (hasOwn(value, '__ob__') && value.__ob__ instanceof Observer) {
  ob = value.__ob__
 } else if (
  shouldObserve &&
  !isServerRendering() &&
  (Array.isArray(value) || isPlainObject(value)) &&
  Object.isExtensible(value) &&
  !value._isVue
 ) {
  ob = new Observer(value)
 }
 if (asRootData && ob) {
  ob.vmCount++
 }
 return ob
}

// src/core/observer/index.js
export class Observer {
 constructor (value) {
  this.value = value
  this.dep = new Dep()
  this.vmCount = 0
  def(value, '__ob__', this)
  if (Array.isArray(value)) {
   if (hasProto) {
    protoAugment(value, arrayMethods)
   } else {
    copyAugment(value, arrayMethods, arrayKeys)
   }
   this.observeArray(value)
  } else {
   this.walk(value)
  }
 }

 /**
  * Walk through all properties and convert them into
  * getter/setters. This method should only be called when
  * value type is Object.
  */
 walk (obj) {
  const keys = Object.keys(obj)
  for (let i = 0; i < keys.length; i++) {
   defineReactive(obj, keys[i])
  }
 }

 /**
  * Observe a list of Array items.
  */
 observeArray (items) {
  for (let i = 0, l = items.length; i < l; i++) {
   observe(items[i])
  }
 }
}

// src/core/observer/array.js
const arrayProto = Array.prototype
export const arrayMethods = Object.create(arrayProto)

const methodsToPatch = [
 'push',
 'pop',
 'shift',
 'unshift',
 'splice',
 'sort',
 'reverse'
]

methodsToPatch.forEach(function (method) {
 // cache original method
 const original = arrayProto[method]
 def(arrayMethods, method, function mutator (...args) {
  const result = original.apply(this, args)
  const ob = this.__ob__
  let inserted
  switch (method) {
   case 'push':
   case 'unshift':
    inserted = args
    break
   case 'splice':
    inserted = args.slice(2)
    break
  }
  if (inserted) ob.observeArray(inserted)
  // notify change
  ob.dep.notify()
  return result
 })
})

if (asRootData && ob) {
  ob.vmCount++
}

...
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) {
  ...
  childOb = !shallow && observe(newVal)
  dep.notify()
 }
})

// src/core/observer/dep.js
export default class Dep {
 static target: ?Watcher;
 id: number;
 subs: Array<Watcher>;

 constructor () {
  this.id = uid++
  this.subs = []
 }

 addSub (sub: Watcher) {
  this.subs.push(sub)
 }

 removeSub (sub: Watcher) {
  remove(this.subs, sub)
 }

 depend () {
  if (Dep.target) {
   Dep.target.addDep(this)
  }
 }

 notify () {
  // stabilize the subscriber list first
  const subs = this.subs.slice()
  ...
  for (let i = 0, l = subs.length; i < l; i++) {
   subs[i].update()
  }
 }
}

if (childOb) {
  childOb.dep.depend()
  if (Array.isArray(value)) {
    dependArray(value)
  }
}

const data = {
  arr: [{
    value: 1
  }],
}

data.a = 1; // 无法触发setter
data.arr[1] = {value: 2}; // 无法触发setter
data.arr.push({value: 3}); // 无法触发setter
data.arr = [{value: 4}]; // 可以触发setter

if (inserted) ob.observeArray(inserted)
// notify change
ob.dep.notify()

// src/core/observer/index.js
export function set (target: Array<any> | Object, key: any, val: any): 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
}

if (Array.isArray(value)) {
  dependArray(value)
}

/**
 * Collect dependencies on array elements when the array is touched, since
 * we cannot intercept array element access like property getters.
 */
function dependArray (value: Array<any>) {
 for (let e, i = 0, l = value.length; i < l; i++) {
  e = value[i]
  e && e.__ob__ && e.__ob__.dep.depend()
  if (Array.isArray(e)) {
   dependArray(e)
  }
 }
}

const data = {
  list: [[{value: 0}]],
};
data.list[0].push({value: 1});

function initComputed (vm: Component, computed: Object) {
 const watchers = vm._computedWatchers = Object.create(null)
 const isSSR = isServerRendering()

 for (const key in computed) {
  const userDef = computed[key]
  const getter = typeof userDef === 'function' ? userDef : userDef.get

  if (!isSSR) {
   // create internal watcher for the computed property.
   watchers[key] = new Watcher(
    vm,
    getter || noop,
    noop,
    computedWatcherOptions
   )
  }
  ...
 }
}

if (!(key in vm)) {
 defineComputed(vm, key, userDef)
}

function createComputedGetter (key) {
 return function computedGetter () {
  const watcher = this._computedWatchers && this._computedWatchers[key]
  if (watcher) {
   if (watcher.dirty) {
    watcher.evaluate()
   }
   if (Dep.target) {
    watcher.depend()
   }
   return watcher.value
  }
 }
}

get () {
 pushTarget(this)
 let value
 const vm = this.vm
 try {
  value = this.getter.call(vm, vm)
 } catch (e) {
  ...
 } finally {
  // "touch" every property so they are all tracked as
  // dependencies for deep watching
  if (this.deep) {
   traverse(value)
  }
  popTarget()
  this.cleanupDeps()
 }
 return value
}

Dep.target = null
const targetStack = []

export function pushTarget (target: ?Watcher) {
 targetStack.push(target)
 Dep.target = target
}

export function popTarget () {
 targetStack.pop()
 Dep.target = targetStack[targetStack.length - 1]
}

addDep (dep: Dep) {
 const id = dep.id
 if (!this.newDepIds.has(id)) {
  this.newDepIds.add(id)
  this.newDeps.push(dep)
  if (!this.depIds.has(id)) {
   dep.addSub(this)
  }
 }
}

if (this.deep) {
 traverse(value)
}

cleanupDeps () {
 let i = this.deps.length
 while (i--) {
  const dep = this.deps[i]
  if (!this.newDepIds.has(dep.id)) {
   dep.removeSub(this)
  }
 }
 ...
}

if (Dep.target) {
 watcher.depend()
}

notify () {
 // stabilize the subscriber list first
 const subs = this.subs.slice()
 for (let i = 0, l = subs.length; i < l; i++) {
  subs[i].update()
 }
}

update () {
 /* istanbul ignore else */
 if (this.lazy) {
  this.dirty = true
 } else if (this.sync) {
  this.run()
 } else {
  queueWatcher(this)
 }
}