vue2从数据变化到视图变化发布订阅模式详解

export function initState (vm: Component) { // ... if (opts.data) { initData(vm) } else { observe(vm._data = {}, true /* asRootData */) } //... } 

function initData (vm: Component) { let data = vm.$options.data data = vm._data = typeof data === 'function' ? getData(data, vm) : data || {} if (!isPlainObject(data)) { data = {} process.env.NODE_ENV !== 'production' && warn( 'data functions should return an object:\n' + 'https://vuejs.org/v2/guide/components.html#data-Must-Be-a-Function', vm ) } // proxy data on instance const keys = Object.keys(data) const props = vm.$options.props const methods = vm.$options.methods let i = keys.length while (i--) { const key = keys[i] if (process.env.NODE_ENV !== 'production') { if (methods && hasOwn(methods, key)) { warn( `Method "${key}" has already been defined as a data property.`, vm ) } } if (props && hasOwn(props, key)) { process.env.NODE_ENV !== 'production' && warn( `The data property "${key}" is already declared as a prop. ` + `Use prop default value instead.`, vm ) } else if (!isReserved(key)) { proxy(vm, `_data`, key) } } // observe data observe(data, true /* asRootData */) } 

/** * Attempt to create an observer instance for a value, * returns the new observer if successfully observed, * or the existing observer if the value already has one. */ export function observe (value: any, asRootData: ?boolean): Observer | void { if (!isObject(value) || value instanceof VNode) { return } let ob: Observer | void 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 } 

/** * Observer class that is attached to each observed * object. Once attached, the observer converts the target * object's property keys into getter/setters that * collect dependencies and dispatch updates. */ export class Observer { value: any; dep: Dep; vmCount: number; // number of vms that have 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)) { 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: Object) { const keys = Object.keys(obj) for (let i = 0; i ) { for (let i = 0, l = items.length; i 

/** * Define a reactive property on an Object. */ 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 const setter = property && property.set if ((!getter || setter) && arguments.length === 2) { val = obj[key] } 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() } // #7981: for accessor properties without setter if (getter && !setter) return if (setter) { setter.call(obj, newVal) } else { val = newVal } childOb = !shallow && observe(newVal) dep.notify() } }) } 

import type Watcher from './watcher' import { remove } from '../util/index' import config from '../config' let uid = 0 /** * A dep is an observable that can have multiple * directives subscribing to it. */ 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) { Dep.target.addDep(this) } } notify () { // stabilize the subscriber list first const subs = this.subs.slice() if (process.env.NODE_ENV !== 'production' && !config.async) { // subs aren't sorted in scheduler if not running async // we need to sort them now to make sure they fire in correct // order subs.sort((a, b) => a.id - b.id) } for (let i = 0, l = subs.length; i 

Object.defineProperty(obj, key, { enumerable: true, configurable: true, get: function reactiveGetter () { // 当访问属性的时候，进行订阅者的收集 }, set: function reactiveSetter (newVal) { // 当修改属性的时候，收到发布者消息的时候进行相应的操作 } }) 

let uid = 0 /** * A watcher parses an expression, collects dependencies, * and fires callback when the expression value changes. * This is used for both the $watch() api and directives. */ export default class Watcher { vm: Component; expression: string; cb: Function; id: number; deep: boolean; user: boolean; lazy: boolean; sync: boolean; dirty: boolean; active: boolean; deps: Array; newDeps: Array; depIds: SimpleSet; newDepIds: SimpleSet; before: ?Function; getter: Function; value: any; constructor ( vm: Component, expOrFn: string | Function, cb: Function, options?: ?Object, isRenderWatcher?: boolean ) { this.vm = vm if (isRenderWatcher) { vm._watcher = this } vm._watchers.push(this) // options if (options) { this.deep = !!options.deep this.user = !!options.user this.lazy = !!options.lazy this.sync = !!options.sync this.before = options.before } else { this.deep = this.user = this.lazy = this.sync = false } this.cb = cb this.id = ++uid // uid for batching this.active = true this.dirty = this.lazy // for lazy watchers this.deps = [] this.newDeps = [] this.depIds = new Set() this.newDepIds = new Set() this.expression = process.env.NODE_ENV !== 'production' ? expOrFn.toString() : '' // parse expression for getter if (typeof expOrFn === 'function') { this.getter = expOrFn } else { this.getter = parsePath(expOrFn) if (!this.getter) { this.getter = noop process.env.NODE_ENV !== 'production' && warn( `Failed watching path: "${expOrFn}" ` + 'Watcher only accepts simple dot-delimited paths. ' + 'For full control, use a function instead.', vm ) } } this.value = this.lazy ? undefined : this.get() } /** * Evaluate the getter, and re-collect dependencies. */ get () { pushTarget(this) let value const vm = this.vm try { value = this.getter.call(vm, vm) } catch (e) { if (this.user) { handleError(e, vm, `getter for watcher "${this.expression}"`) } else { throw 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 } // watcher还有很多其他自定义方法，用的时候再列举 } 

updateComponent = () => { vm._update(vm._render(), hydrating) } 

    /** * Add a dependency to this directive. */ 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) } } } 

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

notify () { // stabilize the subscriber list first const subs = this.subs.slice() if (process.env.NODE_ENV !== 'production' && !config.async) { // subs aren't sorted in scheduler if not running async // we need to sort them now to make sure they fire in correct // order subs.sort((a, b) => a.id - b.id) } for (let i = 0, l = subs.length; i 

/** * Subscriber interface. * Will be called when a dependency changes. */ update () { /* istanbul ignore else */ if (this.lazy) { this.dirty = true } else if (this.sync) { this.run() } else { queueWatcher(this) } } 

/** * Push a watcher into the watcher queue. * Jobs with duplicate IDs will be skipped unless it's * pushed when the queue is being flushed. */ export function queueWatcher (watcher: Watcher) { const id = watcher.id if (has[id] == null) { has[id] = true if (!flushing) { queue.push(watcher) } else { // if already flushing, splice the watcher based on its id // if already past its id, it will be run next immediately. let i = queue.length - 1 while (i > index && queue[i].id > watcher.id) { i-- } queue.splice(i + 1, 0, watcher) } // queue the flush if (!waiting) { waiting = true if (process.env.NODE_ENV !== 'production' && !config.async) { flushSchedulerQueue() return } nextTick(flushSchedulerQueue) } } } 

/** * Flush both queues and run the watchers. */ function flushSchedulerQueue () { currentFlushTimestamp = getNow() flushing = true let watcher, id // Sort queue before flush. // This ensures that: // 1. Components are updated from parent to child. (because parent is always //    created before the child) // 2. A component's user watchers are run before its render watcher (because //    user watchers are created before the render watcher) // 3. If a component is destroyed during a parent component's watcher run, //    its watchers can be skipped. queue.sort((a, b) => a.id - b.id) // do not cache length because more watchers might be pushed // as we run existing watchers for (index = 0; index  MAX_UPDATE_COUNT) { warn( 'You may have an infinite update loop ' + ( watcher.user ? `in watcher with expression "${watcher.expression}"` : `in a component render function.` ), watcher.vm ) break } } } // keep copies of post queues before resetting state const activatedQueue = activatedChildren.slice() const updatedQueue = queue.slice() resetSchedulerState() // call component updated and activated hooks callActivatedHooks(activatedQueue) callUpdatedHooks(updatedQueue) // devtool hook /* istanbul ignore if */ if (devtools && config.devtools) { devtools.emit('flush') } } function callUpdatedHooks (queue) { let i = queue.length while (i--) { const watcher = queue[i] const vm = watcher.vm if (vm._watcher === watcher && vm._isMounted && !vm._isDestroyed) { callHook(vm, 'updated') } } } 

/** * Scheduler job interface. * Will be called by the scheduler. */ run () { if (this.active) { const value = this.get() if ( value !== this.value || // Deep watchers and watchers on Object/Arrays should fire even // when the value is the same, because the value may // have mutated. isObject(value) || this.deep ) { // set new value const oldValue = this.value this.value = value if (this.user) { try { this.cb.call(this.vm, value, oldValue) } catch (e) { handleError(e, this.vm, `callback for watcher "${this.expression}"`) } } else { this.cb.call(this.vm, value, oldValue) } } } } 

 /** * Clean up for dependency collection. */ cleanupDeps () { let i = this.deps.length while (i--) { const dep = this.deps[i] if (!this.newDepIds.has(dep.id)) { dep.removeSub(this) } } let tmp = this.depIds this.depIds = this.newDepIds this.newDepIds = tmp this.newDepIds.clear() tmp = this.deps this.deps = this.newDeps this.newDeps = tmp this.newDeps.length = 0 }