Read / Listen

For a working demo checkout: Demo, or Code

Method Documentation

All reads done by Firestore-Extended is using snapshotChanges().

This is done for the following reasons:

Allows the user to listen for changes to the document / collection being read / listened to, making sure the data is always up to date.
Gives access to additional data that can be added to the data being read, such as:
- id: string => the id of the document
- ref: DocumentReference => the Firestore document reference
- path: string => A string representing the path of the referenced document (relative to the root of the database).
- isExists: boolean => False if document does not exist, applicable when DocNotExistAction.RETURN_ALL_BUT_DATA is used.

These properties are added as the property firestoreMetadata to the returned object when a document is read but will not be saved to firestore. An object of type T that contains the additional firestoreMetadata has the type FireItem<T>.

FireItem is the type that is returned by all methods that return data from firestore.

Listen for Document with sub collections.

listenForRestaurantById$(restaurantId: string): Observable <FireItem<RestaurantItem>> {
    const docRef: DocumentReference <RestaurantItem> = getDocRefWithId(this.restaurantCollectionRef, restaurantId);
    return this.firestoreExt.listenForDoc$<RestaurantItem>(docRef, restaurantSubCollectionQueries);
}

If you do not with to listen for changes and instead just get the firestore data once, you can use take(1):

getRestaurantById$(restaurantId: string): Observable <FireItem<RestaurantItem>> {
    const docRef: DocumentReference <RestaurantItem> = getDocRefWithId(this.restaurantCollectionRef, restaurantId);
    return this.firestoreExt.listenForDoc$<RestaurantItem>(docRef, restaurantSubCollectionQueries).pipe(
        take(1) // this makes sure that the observable stops after returning
    );
}

Listen for Collection without listening for sub collections, notice the Partial:

listenForRestaurants$(): Observable <FireItem<Partial<RestaurantItem>> [] > {
    return this.firestoreExt.listenForCollection$<RestaurantItem>(this.restaurantCollectionFs);
}

Sub Collection Queries used in the examples.

SubCollectionQuery documentation

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
    ]
  },
];

Models used in the examples.

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;
}