类型 void 上不存在 Angular 属性订阅

Question

Currently I am getting a firebase document from my component ts file. It is working perfectly. But when I am trying to move the logic to my service file then trying to subscribe that method from the service in my component getting an error Property subscribe does not exist on type void. Because I think onAuthStateChanged method returns void. In this case how can i get the currently logged in user uid.

Service.ts -

getPetsForCurrentUser(){
this.afAuth.auth.onAuthStateChanged((user) =>{
  if(user){
      // this.afs.collection('pets', ref => ref.where('OwnerID', '==', user.uid)).
      this.afs.collection('pets', ref => ref.where('OwnerID', '==', user.uid)).snapshotChanges().pipe(
        map(actions => actions.map(a => {
          const data = a.payload.doc.data();
          const id = a.payload.doc.id;
          return { id, ...data };
        }))
      ).subscribe(docs => {
        // loop through each item in the array and log value
        docs.forEach(doc => {
          return doc;
        });
      });

  }else {
    console.log("No user logged in");
  }
});

Component.ts -

public allPets : any = [];

  constructor(private petservice : PetService) { }

  ngOnInit() {
    this.petservice.getPetsForCurrentUser().subscribe(res => console.log(res));
  }

Answer 1

Inside the component.ts, you can call onAuthStateChanged , inside ngOnInit , do the following:

  ngOnInit() {
   this.afAuth.auth.onAuthStateChanged((user) =>{
    if(user){
          this.petservice.getPetsForCurrentUser(user).subscribe(res => console.log(res));
       }
     });
  }

Then inisde the service, do the following:

getPetsForCurrentUser(user){
      return this.afs.collection('pets', ref => ref.where('OwnerID', '==', user.uid)).snapshotChanges().pipe(
        map(actions => actions.map(a => {
          const data = a.payload.doc.data();
          const id = a.payload.doc.id;
          return { id, ...data };
        }))
      );
});