- A+
所属分类：Web前端
前言
前面我们简单的了解了 vue 初始化时的一些大概的流程，这里我们详细的了解下具体的内容;
内容
这一块主要围绕init.ts中的initState进行剖析，初始化生命周期之后紧接着。
initState
initState的方法位于scr/core/instance/state.ts中；
const sharedPropertyDefinition = { enumerable: true, configurable: true, get: noop, set: noop } export function proxy(target: Object, sourceKey: string, key: string) { // get方法 sharedPropertyDefinition.get = function proxyGetter() { return this[sourceKey][key] } // set方法 sharedPropertyDefinition.set = function proxySetter(val) { this[sourceKey][key] = val } Object.defineProperty(target, key, sharedPropertyDefinition) } export function initState(vm: Component) { const opts = vm.$options // 存在props则初始化props if (opts.props) initProps(vm, opts.props) // Composition API // 初始化组合式API initSetup(vm) // 存在方法则初始化方法 if (opts.methods) initMethods(vm, opts.methods) // 存在data则初始化data if (opts.data) { initData(vm) } else { const ob = observe((vm._data = {})) ob && ob.vmCount++ } // 存在计算属性则初始化计算属性 if (opts.computed) initComputed(vm, opts.computed) // 存在监听且监听不等于nativeWatch（这个主要是针对火狐浏览器进行处理）则初始化监听 if (opts.watch && opts.watch !== nativeWatch) { initWatch(vm, opts.watch) } } function initProps(vm: Component, propsOptions: Object) { const propsData = vm.$options.propsData || {} const props = (vm._props = shallowReactive({})) // cache prop keys so that future props updates can iterate using Array // instead of dynamic object key enumeration. // 缓存prop的keys以便将来更新props时可以使用数组代替动态的迭代对象key const keys: string[] = (vm.$options._propKeys = []) // 判断是否是根组件 const isRoot = !vm.$parent // root instance props should be converted if (!isRoot) { // 如果不是根组件就关闭响应式处理,防止defineReactive做响应式处理 toggleObserving(false) } for (const key in propsOptions) { keys.push(key) // 对prop数据进行校验 const value = validateProp(key, propsOptions, propsData, vm) /* istanbul ignore else */ if (__DEV__) { const hyphenatedKey = hyphenate(key) // 检查属性是否是保留属性 if ( isReservedAttribute(hyphenatedKey) || config.isReservedAttr(hyphenatedKey) ) { warn( `"${hyphenatedKey}" is a reserved attribute and cannot be used as component prop.`, vm ) } defineReactive(props, key, value, () => { if (!isRoot && !isUpdatingChildComponent) { warn( `Avoid mutating a prop directly since the value will be ` + `overwritten whenever the parent component re-renders. ` + `Instead, use a data or computed property based on the prop's ` + `value. Prop being mutated: "${key}"`, vm ) } }) } else { 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. // 在Vue.extend（）过程中，静态props已经在组件的原型上被代理。我们只需要在这里实例化时代理定义的props。 if (!(key in vm)) { proxy(vm, `_props`, key) } } // 开启响应式处理 toggleObserving(true) } /** * 初始化data * @param vm */ function initData(vm: Component) { let data: any = vm.$options.data // 通过getData将函数转为对象 data = vm._data = isFunction(data) ? getData(data, vm) : data || {} if (!isPlainObject(data)) { data = {} // https://v2.cn.vuejs.org/v2/guide/components.html#data-%E5%BF%85%E9%A1%BB%E6%98%AF%E4%B8%80%E4%B8%AA%E5%87%BD%E6%95%B0 // 一个组件的 data 选项必须是一个函数，因此每个实例可以维护一份被返回对象的独立的拷贝 // 避免了实例之间相互影响 __DEV__ && warn( 'data functions should return an object:n' + 'https://v2.vuejs.org/v2/guide/components.html#data-Must-Be-a-Function', vm ) } // proxy data on instance const keys = Object.keys(data) const props = vm.$options.props const methods = vm.$options.methods let i = keys.length while (i--) { const key = keys[i] // 检查key名是否在methods中已经使用 if (__DEV__) { if (methods && hasOwn(methods, key)) { warn(`Method "${key}" has already been defined as a data property.`, vm) } } // 检查key名是否在props中使用 if (props && hasOwn(props, key)) { __DEV__ && warn( `The data property "${key}" is already declared as a prop. ` + `Use prop default value instead.`, vm ) // 检查key名是否符合规范,即不以$和_开头 } else if (!isReserved(key)) { // 代理数据 |本质上还是 Object.defineProperty proxy(vm, `_data`, key) } } // observe data | 响应式数据 const ob = observe(data) ob && ob.vmCount++ } /** * 获取data内容|转为对象 * @param data * @param vm * @returns */ export function getData(data: Function, vm: Component): any { // #7573 disable dep collection when invoking data getters pushTarget() try { return data.call(vm, vm) } catch (e: any) { handleError(e, vm, `data()`) return {} } finally { popTarget() } } const computedWatcherOptions = { lazy: true } function initComputed(vm: Component, computed: Object) { // $flow-disable-line // 创建一个空对象 const watchers = (vm._computedWatchers = Object.create(null)) // computed properties are just getters during SSR // 计算的内容只是SSR期间的getter // 是否服务端渲染 const isSSR = isServerRendering() for (const key in computed) { const userDef = computed[key] const getter = isFunction(userDef) ? userDef : userDef.get if (__DEV__ && getter == null) { warn(`Getter is missing for computed property "${key}".`, vm) } if (!isSSR) { // create internal watcher for the computed property. // 不是服务端渲染,就为计算属性创建内部观察程序。 // noop 空函数：function() {} watchers[key] = new Watcher( vm, getter || noop, noop, computedWatcherOptions ) } // component-defined computed properties are already defined on the // component prototype. We only need to define computed properties defined // at instantiation here. // 组件定义的计算内容已经在组件原型上定义。我们只需要在这里定义实例化时定义的计算内容。 if (!(key in vm)) { defineComputed(vm, key, userDef) } else if (__DEV__) { // 开发环境下检查key名是否被过早的定义在data,props,methods中 if (key in vm.$data) { warn(`The computed property "${key}" is already defined in data.`, vm) } else if (vm.$options.props && key in vm.$options.props) { warn(`The computed property "${key}" is already defined as a prop.`, vm) } else if (vm.$options.methods && key in vm.$options.methods) { warn( `The computed property "${key}" is already defined as a method.`, vm ) } } } } export function defineComputed( target: any, key: string, userDef: Record<string, any> | (() => any) ) { // 是否服务端渲染 const shouldCache = !isServerRendering() // 定义get和set if (isFunction(userDef)) { sharedPropertyDefinition.get = shouldCache ? createComputedGetter(key) : createGetterInvoker(userDef) sharedPropertyDefinition.set = noop } else { sharedPropertyDefinition.get = userDef.get ? shouldCache && userDef.cache !== false ? createComputedGetter(key) : createGetterInvoker(userDef.get) : noop sharedPropertyDefinition.set = userDef.set || noop } if (__DEV__ && sharedPropertyDefinition.set === noop) { sharedPropertyDefinition.set = function () { warn( `Computed property "${key}" was assigned to but it has no setter.`, this ) } } Object.defineProperty(target, key, sharedPropertyDefinition) } function createComputedGetter(key) { return function computedGetter() { const watcher = this._computedWatchers && this._computedWatchers[key] if (watcher) { // 是否被计算过,如果dirty为true表明未被计算过 if (watcher.dirty) { watcher.evaluate() // 调用watcher.get方法,值会保存在watcher.value上 } if (Dep.target) { if (__DEV__ && Dep.target.onTrack) { Dep.target.onTrack({ effect: Dep.target, target: this, type: TrackOpTypes.GET, key }) } watcher.depend() } return watcher.value } } } function createGetterInvoker(fn) { return function computedGetter() { return fn.call(this, this) } } function initMethods(vm: Component, methods: Object) { const props = vm.$options.props // 循环遍历methods for (const key in methods) { if (__DEV__) { // 不是函数类型发出警告 if (typeof methods[key] !== 'function') { warn( `Method "${key}" has type "${typeof methods[ key ]}" in the component definition. ` + `Did you reference the function correctly?`, vm ) } // 函数名称和props中的是否冲突 if (props && hasOwn(props, key)) { warn(`Method "${key}" has already been defined as a prop.`, vm) } // 函数名不能以_和$开头 if (key in vm && isReserved(key)) { warn( `Method "${key}" conflicts with an existing Vue instance method. ` + `Avoid defining component methods that start with _ or $.` ) } } // 将methods绑定在当前实例上 vm[key] = typeof methods[key] !== 'function' ? noop : bind(methods[key], vm) } } function initWatch(vm: Component, watch: Object) { // 遍历watch for (const key in watch) { const handler = watch[key] // 是否是数组 if (isArray(handler)) { // 循环创建watcher监听回调函数 for (let i = 0; i < handler.length; i++) { createWatcher(vm, key, handler[i]) } } else { // 创建watcher监听回调函数 createWatcher(vm, key, handler) } } } function createWatcher( vm: Component, expOrFn: string | (() => any), handler: any, options?: Object ) { // 检查是否是普通对象 if (isPlainObject(handler)) { // 将handler挂载到options属性上 options = handler // 提取handler属性赋值给handler handler = handler.handler } // 是否是字符串 if (typeof handler === 'string') { // 从实例中找到handler赋值给handler handler = vm[handler] } // 实例上的$watch方法 return vm.$watch(expOrFn, handler, options) } 
