官方实现

2023年06月11日

柏拉文

越努力，越幸运

一、src/core/index.ts

---

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'
import { version } from 'v3'

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

二、src/core/global-api/index.ts initGlobalAPI()

---

/**
 * 初始化 Vue 的众多全局 API，比如：
 *   默认配置：Vue.config
 *   工具方法：Vue.util.xx
 *   Vue.set、Vue.delete、Vue.nextTick、Vue.observable
 *   Vue.options.components、Vue.options.directives、Vue.options.filters、Vue.options._base
 *   Vue.use、Vue.extend、Vue.mixin、Vue.component、Vue.directive、Vue.filter
 *   
 */

export function initGlobalAPI(Vue: GlobalAPI) {
  // config
  const configDef: Record<string, any> = {}
  configDef.get = () => config
  if (__DEV__) {
    configDef.set = () => {
      warn(
        'Do not replace the Vue.config object, set individual fields instead.'
      )
    }
  }
  Object.defineProperty(Vue, 'config', configDef)

  // exposed util methods.
  // NOTE: these are not considered part of the public API - avoid relying on
  // them unless you are aware of the risk.
  Vue.util = {
    warn,
    extend,
    mergeOptions,
    defineReactive
  }

  Vue.set = set
  Vue.delete = del
  Vue.nextTick = nextTick

  // 2.6 explicit observable API
  Vue.observable = <T>(obj: T): T => {
    observe(obj)
    return obj
  }

  Vue.options = Object.create(null)
  ASSET_TYPES.forEach(type => {
    Vue.options[type + 's'] = Object.create(null)
  })

  // this is used to identify the "base" constructor to extend all plain-object
  // components with in Weex's multi-instance scenarios.
  Vue.options._base = Vue

   // 在 Vue.options.components 中添加内置组件，比如 keep-alive
  extend(Vue.options.components, builtInComponents)

  initUse(Vue)
  initMixin(Vue)
  initExtend(Vue)
  initAssetRegisters(Vue)
}

三、src/core/observer/index.ts set()

---

/**
 * 通过 Vue.set 或者 this.$set 方法给 target 的指定 key 设置值 val
 * 如果 target 是对象，并且 key 原本不存在，则为新 key 设置响应式，然后执行依赖通知
 */

export function set(
  target: any[] | Record<string, any>,
  key: any,
  val: any
): any {
  if (__DEV__ && (isUndef(target) || isPrimitive(target))) {
    warn(
      `Cannot set reactive property on undefined, null, or primitive value: ${target}`
    )
  }
  if (isReadonly(target)) {
    __DEV__ && warn(`Set operation on key "${key}" failed: target is readonly.`)
    return
  }
  const ob = (target as any).__ob__
  // 更新数组指定下标的元素，Vue.set(array, idx, val)，通过 splice 方法实现响应式更新
  if (isArray(target) && isValidArrayIndex(key)) {
    target.length = Math.max(target.length, key)
    target.splice(key, 1, val)
    // when mocking for SSR, array methods are not hijacked
    if (ob && !ob.shallow && ob.mock) {
      observe(val, false, true)
    }
    return val
  }
  // 更新对象已有属性，Vue.set(obj, key, val)，执行更新即可
  if (key in target && !(key in Object.prototype)) {
    target[key] = val
    return val
  }
  // 不能向 Vue 实例或者 $data 添加动态添加响应式属性，vmCount 的用处之一，
  // this.$data 的 ob.vmCount = 1，表示根组件，其它子组件的 vm.vmCount 都是 0
  if ((target as any)._isVue || (ob && ob.vmCount)) {
    __DEV__ &&
      warn(
        'Avoid adding reactive properties to a Vue instance or its root $data ' +
          'at runtime - declare it upfront in the data option.'
      )
    return val
  }
  // target 不是响应式对象，新属性会被设置，但是不会做响应式处理
  if (!ob) {
    target[key] = val
    return val
  }
  // 给对象定义新属性，通过 defineReactive 方法设置响应式，并触发依赖更新
  defineReactive(ob.value, key, val, undefined, ob.shallow, ob.mock)
  if (__DEV__) {
    ob.dep.notify({
      type: TriggerOpTypes.ADD,
      target: target,
      key,
      newValue: val,
      oldValue: undefined
    })
  } else {
    ob.dep.notify()
  }
  return val
}