Failure in retrieving values from AngularFire2 Subscribe

Question

Failure in retrieving values from AngularFire2 Subscribe

I am encountering an issue with the code in my authService

    constructor(
    private afAuth: AngularFireAuth,
    private db: AngularFireDatabase,
    private router: Router
  ) {
    this.authState = afAuth.authState;
    this.authState.subscribe((user: firebase.User) => {
        this.authState = user;
    });
    if ( this.authenticated ) {
      // this.router.navigate([`/content`]);
    }
  }

  // Returns true if user is logged in
  get authenticated(): any {
    return this.authState;
  }

When I call the get authenticated method, it returns undefined:

COMPONENT

    constructor(
    private auth: AuthService
  ) {
      this.currentUser = this.auth.authenticated;
  }
showUser() {
    console.log(this.currentUser.uid);
  }

I am looking for assistance on resolving this issue, any suggestions?

angular typescript firebase rxjs observable

Answer 1

Answer №1

Typically, what occurs is considered normal. The console.log function operates synchronously, while the content within the subscription runs asynchronously. Therefore, even though the console.log appears after the .subscribe method, it may be executed faster in reality. This explains why

console.log( this.authState.uid );

outputs undefined.

In addition, it is recommended to refrain from including any logic in the contructor.

It would be more beneficial to have the .subscribe in OnInit() and attempt to access the this.authState in the AfterViewInit() lifecycle.

One last point to mention, you can also store the subscription created in OnInit and utilize .unsubscribe in OnDestroy :)

Answer 2

Typically, what occurs is considered normal. The console.log function operates synchronously, while the content within the subscription runs asynchronously. Therefore, even though the console.log appears after the .subscribe method, it may be executed faster in reality. This explains why

console.log( this.authState.uid );

outputs undefined.

In addition, it is recommended to refrain from including any logic in the contructor.

It would be more beneficial to have the .subscribe in OnInit() and attempt to access the this.authState in the AfterViewInit() lifecycle.

One last point to mention, you can also store the subscription created in OnInit and utilize .unsubscribe in OnDestroy :)

Answer 3

Answer №2

What is your goal? What are you looking for and why?

I am still uncertain about the rationale behind this requirement. However, it appears to be related to a lifecycle hook issue (you can refer to the documentation here).

Try implementing it in the following manner with your component:

export class *YOUR_COMPONENT* implements OnInit {

   private authenticatedUser$: Subscription; // import rxjs/Subscription
   private authenticatedUser: User; // import firebase/app

   constructor(private auth: AuthService) {
     this.authenticatedUser$ = this.auth.getAuthenticatedUser().subscribe((user: User) => {
      // Save the Firebase user in the 'authenticatedUser' variable here
      this.authenticatedUser = user;
   });

   ngOnInit() {
      // Check if the user is logged in..
      if(this.authenticatedUser) {
        // Write your logic here when user is logged in
      }
   }

   ....}

Here is an example of your authService:

export class AuthService {

     constructor(private afAuth: AngularFireAuth) { //import angularfire2/auth/auth
       // Constructor is empty
     });

     getAuthenticatedUser() {
       return this.auth.authState;
     }

   ....}

This approach should resolve the issue.

Answer 4

What is your goal? What are you looking for and why?

I am still uncertain about the rationale behind this requirement. However, it appears to be related to a lifecycle hook issue (you can refer to the documentation here).

Try implementing it in the following manner with your component:

export class *YOUR_COMPONENT* implements OnInit {

   private authenticatedUser$: Subscription; // import rxjs/Subscription
   private authenticatedUser: User; // import firebase/app

   constructor(private auth: AuthService) {
     this.authenticatedUser$ = this.auth.getAuthenticatedUser().subscribe((user: User) => {
      // Save the Firebase user in the 'authenticatedUser' variable here
      this.authenticatedUser = user;
   });

   ngOnInit() {
      // Check if the user is logged in..
      if(this.authenticatedUser) {
        // Write your logic here when user is logged in
      }
   }

   ....}

Here is an example of your authService:

export class AuthService {

     constructor(private afAuth: AngularFireAuth) { //import angularfire2/auth/auth
       // Constructor is empty
     });

     getAuthenticatedUser() {
       return this.auth.authState;
     }

   ....}

This approach should resolve the issue.

Answer 5

Answer №3

When working with AngularFireAuth.authState

, it's important to understand that it operates asynchronously as an Observable. If you're unfamiliar with Observables, you can learn more about them on the ReactiveX site.

In essence, the authState observable represents a sequence of values that unfold over time. It works asynchronously, meaning there is a delay in resolving its value, and it's lazy - requiring subscription to retrieve a value (which explains why your console.log isn't functioning outside).

If you find yourself needing access to the "current" value without being inside a subscribe block, I suggest using a BehaviorSubject. For further insight into subjects, refer to the ReactiveX documentation:

currentAuthState: BehaviorSubject<firebase.User|null|undefined>;

constructor(afAuth: AngularFireAuth) {
  this.currentAuthState = new BehaviorSubject(undefined);
  afAuth.authState.subscribe(this.currentAuthState);
}

With this setup, you can utilize this.currentAuthState.getValue() to check the current value, .subscribe for monitoring changes, employ various RxJS operators like map, do, switchMap, etc., and integrate async pipes in your view with

{{ (currentAuthState | async)?.email }}

.

The value will be undefined during loading, null when no user is logged in, and a firebase.User object when a user is authenticated.

Answer 6

When working with AngularFireAuth.authState

, it's important to understand that it operates asynchronously as an Observable. If you're unfamiliar with Observables, you can learn more about them on the ReactiveX site.

In essence, the authState observable represents a sequence of values that unfold over time. It works asynchronously, meaning there is a delay in resolving its value, and it's lazy - requiring subscription to retrieve a value (which explains why your console.log isn't functioning outside).

If you find yourself needing access to the "current" value without being inside a subscribe block, I suggest using a BehaviorSubject. For further insight into subjects, refer to the ReactiveX documentation:

currentAuthState: BehaviorSubject<firebase.User|null|undefined>;

constructor(afAuth: AngularFireAuth) {
  this.currentAuthState = new BehaviorSubject(undefined);
  afAuth.authState.subscribe(this.currentAuthState);
}

With this setup, you can utilize this.currentAuthState.getValue() to check the current value, .subscribe for monitoring changes, employ various RxJS operators like map, do, switchMap, etc., and integrate async pipes in your view with

{{ (currentAuthState | async)?.email }}

.

The value will be undefined during loading, null when no user is logged in, and a firebase.User object when a user is authenticated.

Failure in retrieving values from AngularFire2 Subscribe

Answer №1

Answer №2

Answer №3

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