vue中的数据绑定原理的实现

Vue.prototype._init = function (options?: Object) {
...
initLifecycle(vm)
initEvents(vm)
callHook(vm,'beforeCreate')
initState(vm)
callHook(vm,'created')
initRender(vm)
}

export function initState (vm: Component) {
vm._watchers = []
initProps(vm)
initData(vm)
initComputed(vm)
initMethods(vm)
initWatch(vm)
}

function initData (vm: Component) {
let data = vm.$options.data
data = vm._data = typeof data === 'function'
? data.call(vm)
: data || {}
if (!isPlainObject(data)) {
data = {}
process.env.NODE_ENV !== 'production' && warn(
'data functions should return an object.',vm
)
}
// proxy data on instance
const keys = Object.keys(data)
const props = vm.$options.props
let i = keys.length
while (i--) {
if (props && hasOwn(props,keys[i])) {
process.env.NODE_ENV !== 'production' && warn(
The data property "${keys[i]}" is already declared as a prop. +
Use prop default value instead.,vm
)
} else {
proxy(vm,keys[i])
}
}
// observe data
observe(data)
data.ob && data.ob.vmCount++
}

export function observe (value: any): Observer | void {
if (!isObject(value)) {
return
}
let ob: Observer | void
if (hasOwn(value,'ob') && value.ob instanceof Observer) {
ob = value.ob
} else if (
observerState.shouldConvert &&
!config._isServer &&
(Array.isArray(value) || isPlainObject(value)) &&
Object.isExtensible(value) &&
!value._isVue
) {
ob = new Observer(value)
}
return ob
}

export class Observer {
value: any;
dep: Dep;
vmCount: number; // number of vms that has this object as root $data

constructor (value: any) {
this.value = value
this.dep = new Dep()
this.vmCount = 0
def(value,'ob',this)
if (Array.isArray(value)) {
const augment = hasProto
? protoAugment
: copyAugment
augment(value,arrayMethods,arrayKeys)
this.observeArray(value)
} else {
this.walk(value)
}
}

/**

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

/**

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

export function defineReactive (
obj: Object,key: string,val: any,customSetter?: Function
) {
const dep = new Dep()
// data中的每一个成员都有一个对应的Dep，在此闭包创建。

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

let childOb = 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() // 依赖收集
if (childOb) {
childOb.dep.depend()
}
if (Array.isArray(value)) {
for (let e,i = 0,l = value.length; i < l; i++) {
e = value[i]
e && e.ob && e.ob.dep.depend()
}
}
}
return value
},set: function reactiveSetter (newVal) {
const value = getter ? getter.call(obj) : val
if (newVal === value) {
return
}
if (process.env.NODE_ENV !== 'production' && customSetter) {
customSetter()
}
if (setter) {
setter.call(obj,newVal)
} else {
val = newVal
}
childOb = observe(newVal)
dep.notify() // 发布通知
}
})
}

export default class Dep {
static target: ?Watcher;
id: number;
subs: Array;

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

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

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

depend () {
if (Dep.target) {
// 调用当前target，也就是正在处理的watcher的addDep方法，并把此Dep传进去
Dep.target.addDep(this)
}
}

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

export default class Watcher {
...
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)) {
// 将当前watcher添加到当前的Dep中
dep.addSub(this)
}
}
}
...
}