catCount: Observable;
  dogName: Observable;

  ngOnInit() {

    this.catCount = this.db.list('/cats')
    .map(cats => {
      return cats.length
      })

      this.dogName = this.db.object('/dogs/-KpRuD47u8810-BXEn5Q')
      .map(dog => {
        return dog.name
     })
    }