vue/src/core/observer/index.ts

import Dep from './dep'
import VNode from '../vdom/vnode'
import { arrayMethods } from './array'
import {
  def,
  warn,
  hasOwn,
  isArray,
  hasProto,
  isObject,
  isPlainObject,
  isPrimitive,
  isUndef,
  isValidArrayIndex,
  isServerRendering,
  hasChanged
} from '../util/index'
import { isReadonly, isRef } from '../../v3'

const arrayKeys = Object.getOwnPropertyNames(arrayMethods)

/**
 * In some cases we may want to disable observation inside a component's
 * update computation.
 */
export let shouldObserve: boolean = true

export function toggleObserving(value: boolean) {
  shouldObserve = value
}

/**
 * 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 {
  dep: Dep
  vmCount: number // number of vms that have this object as root $data

  constructor(public value: any, public shallow = false) {
    // this.value = value
    this.dep = new Dep()
    this.vmCount = 0
    def(value, '__ob__', this)
    if (isArray(value)) {
      if (hasProto) {
        protoAugment(value, arrayMethods)
      } else {
        copyAugment(value, arrayMethods, arrayKeys)
      }
      if (!shallow) {
        this.observeArray(value)
      }
    } else {
      this.walk(value, shallow)
    }
  }

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

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

// helpers

/**
 * Augment a target Object or Array by intercepting
 * the prototype chain using __proto__
 */
function protoAugment(target, src: Object) {
  /* eslint-disable no-proto */
  target.__proto__ = src
  /* eslint-enable no-proto */
}

/**
 * Augment a target Object or Array by defining
 * hidden properties.
 */
/* istanbul ignore next */
function copyAugment(target: Object, src: Object, keys: Array<string>) {
  for (let i = 0, l = keys.length; i < l; i++) {
    const key = keys[i]
    def(target, key, src[key])
  }
}

/**
 * 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, shallow?: boolean): Observer | void {
  if (!isObject(value) || isRef(value) || value instanceof VNode) {
    return
  }
  let ob: Observer | void
  if (hasOwn(value, '__ob__') && value.__ob__ instanceof Observer) {
    ob = value.__ob__
  } else if (
    shouldObserve &&
    !isServerRendering() &&
    (isArray(value) || isPlainObject(value)) &&
    Object.isExtensible(value) &&
    !value.__v_skip
  ) {
    ob = new Observer(value, shallow)
  }
  return ob
}

/**
 * Define a reactive property on an Object.
 */
export function defineReactive(
  obj: object,
  key: string,
  val?: any,
  customSetter?: Function | null,
  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 (isArray(value)) {
            dependArray(value)
          }
        }
      }
      return isRef(value) ? value.value : value
    },
    set: function reactiveSetter(newVal) {
      const value = getter ? getter.call(obj) : val
      if (!hasChanged(value, newVal)) {
        return
      }
      if (__DEV__ && customSetter) {
        customSetter()
      }
      if (setter) {
        setter.call(obj, newVal)
      } else if (getter) {
        // #7981: for accessor properties without setter
        return
      } else if (isRef(value) && !isRef(newVal)) {
        value.value = newVal
      } else {
        val = newVal
      }
      childOb = !shallow && observe(newVal)
      dep.notify()
    }
  })

  return dep
}

/**
 * Set a property on an object. Adds the new property and
 * triggers change notification if the property doesn't
 * already exist.
 */
export function set(
  target: Array<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
  }
  if (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 as any).__ob__
  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
  }
  if (!ob) {
    target[key] = val
    return val
  }
  defineReactive(ob.value, key, val)
  ob.dep.notify()
  return val
}

/**
 * Delete a property and trigger change if necessary.
 */
export function del(target: Array<any> | Object, key: any) {
  if (__DEV__ && (isUndef(target) || isPrimitive(target))) {
    warn(
      `Cannot delete reactive property on undefined, null, or primitive value: ${target}`
    )
  }
  if (isArray(target) && isValidArrayIndex(key)) {
    target.splice(key, 1)
    return
  }
  const ob = (target as any).__ob__
  if ((target as any)._isVue || (ob && ob.vmCount)) {
    __DEV__ &&
      warn(
        'Avoid deleting properties on a Vue instance or its root $data ' +
          '- just set it to null.'
      )
    return
  }
  if (isReadonly(target)) {
    __DEV__ &&
      warn(`Delete operation on key "${key}" failed: target is readonly.`)
    return
  }
  if (!hasOwn(target, key)) {
    return
  }
  delete target[key]
  if (!ob) {
    return
  }
  ob.dep.notify()
}

/**
 * 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 (isArray(e)) {
      dependArray(e)
    }
  }
}