stateMixin() — vue Function Reference

Source Code

src/core/instance/state.ts lines 341–393

export function stateMixin(Vue: typeof Component) {
  // flow somehow has problems with directly declared definition object
  // when using Object.defineProperty, so we have to procedurally build up
  // the object here.
  const dataDef: any = {}
  dataDef.get = function () {
    return this._data
  }
  const propsDef: any = {}
  propsDef.get = function () {
    return this._props
  }
  if (__DEV__) {
    dataDef.set = function () {
      warn(
        'Avoid replacing instance root $data. ' +
          'Use nested data properties instead.',
        this
      )
    }
    propsDef.set = function () {
      warn(`$props is readonly.`, this)
    }
  }
  Object.defineProperty(Vue.prototype, '$data', dataDef)
  Object.defineProperty(Vue.prototype, '$props', propsDef)

  Vue.prototype.$set = set
  Vue.prototype.$delete = del

  Vue.prototype.$watch = function (
    expOrFn: string | (() => any),
    cb: any,
    options?: Record<string, any>
  ): Function {
    const vm: Component = this
    if (isPlainObject(cb)) {
      return createWatcher(vm, expOrFn, cb, options)
    }
    options = options || {}
    options.user = true
    const watcher = new Watcher(vm, expOrFn, cb, options)
    if (options.immediate) {
      const info = `callback for immediate watcher "${watcher.expression}"`
      pushTarget()
      invokeWithErrorHandling(cb, vm, [watcher.value], vm, info)
      popTarget()
    }
    return function unwatchFn() {
      watcher.teardown()
    }
  }
}