Vue源码学习 计算属性computed about blogs HOT 1 OPEN

update () {
    if (this.computed) {
      ....
        this.getAndInvoke(() => {
          this.dep.notify()
        })
    }
  }

getAndInvoke (cb: Function) {
    const value = this.get()
    if (
      value !== this.value ||
      isObject(value) ||
      this.deep
    ) {
      const oldValue = this.value
      this.value = value
      this.dirty = false
      if (this.user) {
        try {
          cb.call(this.vm, value, oldValue)
        } catch (e) {
          handleError(e, this.vm, `callback for watcher "${this.expression}"`)
        }
      } else {
        cb.call(this.vm, value, oldValue)
      }
    }
  }