Return a sub-collection in firebase using Angular firestore

问题

I have a sub-collection called saved as a nested collection to each user. User has its own fields and a collection of saved which contains two fields and an array. I can display only user fields but i don't know a proper way to access each user sub-collection.

 export class SavedComponent implements OnInit{
  public saved: Saved[];
  public currentUser: any = null;
  public user: User;
  private subscriptions: Subscription[] = [];

  constructor(

    // Adding saved service
    private savedService: SavedService,
    private auth: AuthService,
    private loadingService: LoadingService,
    private route: ActivatedRoute,
    private db: AngularFirestore
  ) {
    // this.loadingService.isLoading.next(true);
}

    this.subscriptions.push(
      this.auth.currentUser.subscribe( user => {
        this.currentUser = user;
        this.loadingService.isLoading.next(false);
        // Console log the current authentiucated user 
        console.log(this.currentUser);
      })
    );

    this.subscriptions.push(
      this.route.paramMap.subscribe( params => {
        const userId = params.get('userId');
        const userRef: AngularFirestoreDocument<User> = this.db.doc(`users/${userId}`);
        userRef.valueChanges().subscribe(user => this.user = user);
      })
    )


   // Example of html template

    <div class="row justify-content-center">
        <div class="col-xs-12 col-sm-8 col-md-6 text-center name">
            {{user?.firstName}} {{user?.lastName}}
        </div>
    </div>

回答1:

As Frank van Puffelen commented, your best bet to access a user's subcollection is

    this.db.collection(`users/${userId}/saved`)

To reach your saved subcollection, you need to first access your user document inside your users collection. As per this Firestore document, a query's structure to access a subcollection's document, you alternate between accessing a collection, then a document, and so on to reach a subcollection, or a subcollection's document.

You cannot reference a collection in a collection or a document in a document.

It is important that you specify this.db.collection for a collection or subcollection, and this.db.doc for a collection's or subcollection's documents.

来源：https://stackoverflow.com/questions/58546545/return-a-sub-collection-in-firebase-using-angular-firestore