editRestaurant$(restaurant: FireItem<RestaurantItem>, data: UpdateData<Partial<RestaurantItem>>): Observable<void> {
    return this.firestoreExt.update$(data, restaurant.firestoreMetadata.ref, restaurantSubCollectionWriters);
}

const restaurantSubCollectionWriters: SubCollectionWriter[] = [
  { name: 'reviews' }, // make reviews a sub collection
  {
    name: 'dishes',  // make dishes a sub collection
    subCollectionWriters: [ // sub collection inside a sub collection
      {name: 'images'} // make images a sub collection inside dishes
    ]
  },
];

const restaurantSubCollectionQueries: SubCollectionQuery[] = [
  // add reviews sub Collection to restaurant object
  {
    name: 'reviews',
    queryConstraints: [
      orderBy('score')
    ]
  },
  { // add dishes sub Collection to restaurant object
    name: 'dishes',
    subCollectionQueries: [
      {name: 'images'} // add images sub Collection to dish object
    ]
  },
];

export interface RestaurantItem {
  name: string;
  category: string;
  averageReviewScore: number;
  address: AddressItem;
  dishes?: DishItem[]; // optional so that we can get just the base object to display in a list
  reviews?: ReviewItem[]; // optional so that we can get just the base object to display in a list
}

export interface AddressItem {
  zipCode: string;
  city: string;
  line1: string;
}

export interface DishItem {
  name: string;
  images: ImageItem[];
}

export interface ImageItem {
  url: string;
}

export interface ReviewItem {
  score: number;
  text: string;
  userName: string;
}