Angular 5 HttpInterceptor Flow

Question

I am trying to implement HttpInterceptor in one of my Angular application to show a spinner on every request. The spinner shows beautifully. However, I also implemented a notificationService which utilizes SweetAlert to display notification modals based on the response from the server. I was able to display a Success modal but not Error modal. My codes are below:

INTERCEPTOR:

 intercept(req: HttpRequest < any > , next: HttpHandler): Observable < HttpEvent < any >> {
 this._spinnerService.requestStarted();
 return next.handle(req).do(
   (event: HttpEvent<any>) => {
     if (event instanceof HttpResponse) {
       this._spinnerService.requestEnded();
     }
   },
   (err: any) => {
     if (err instanceof HttpErrorResponse) {
       this._spinnerService.requestEnded();
     }
   }
 );
}

LOGIN:

login() {
this.spinnerSub = this.spinnerService.spinnerState.subscribe(state => {
  this.showSpinner = state;
});
   const user = {
     email: this.userEmail,
     password: this.userPw
   };

   this.authService.authenticateUser(user).subscribe((data: ILoginResponse) => {
     this.spinnerSub = this.spinnerService.spinnerState.subscribe(state => {
        this.showSpinner = state;
     });
     if (data.success) {
      this.notificationService.showSuccess(data.title, data.message)
        .then((result) => {
          console.log(result);
          this.router.navigate(['/user/dashboard']);
        })
        .catch((reason) => {
          console.log('--> Alert dismissed: ', reason);
        });
     } else {
       this.notificationService.showError(data.title, data.message)
        .then((result) => {
          console.log(result);
        })
        .catch((reason) => {
          console.log('--> Error dismissed: ', reason);
        });
     }
   });
  }

NOTIFICATION SERVICE:

  showSuccess(type, message) {
   return swal({
    title: 'Success',
    text: message,
    type: type
   });
  }

  showError(type, message) {
    return swal({
      title: 'Error',
      text: message,
      type: type
    });
  }

Any help/suggestion would be much appreciated. Thanks.

EDIT: I tried putting the NotificationService, specifically the showError() in the (err:any) block of the Interceptor. Well it works but I want to keep the NotificationService on specific components (like Login), not every requests.

Answer 1

The flow of the Interceptor is to prevent faulsy response coming back from a RestAPI call.

For example in my question above, I check data.success because that is how I set up in my Backend. The Interceptor will make sure you get a truthy response and whatever is categorized as Error will be set as HttpErrorResponse.

this.authService.authenticateUser(user).subscribe(
 (data: ILoginResponse) => {
 console.log(data);
 this.spinnerSub = this.spinnerService.spinnerState.subscribe(state => {
    this.showSpinner = state;
 });
 this.notificationService.showSuccess(data.title, data.message)
    .then((result) => {
      console.log(result);
      this.router.navigate(['/user/dashboard']);
    })
    .catch((reason) => {
      console.log('--> Alert dismissed: ', reason);
    });
   },

   (err: any) => {
      console.log(err);
      this.notificationService.showError('error', 'Just an error'); <- my NotificationService will 
get called here instead of getting called up in the else block like in my question above.
    });