Strategies for dealing with Observable inconsistencies in an Angular application

Question

Strategies for dealing with Observable inconsistencies in an Angular application

Encountering an error during the compilation of my Angular app:

The error message states: Type 'Observable<Promise<void>>' is not compatible with type 'Observable<AuthResponseData>'. The issue lies in 'Promise' lacking properties such as kind, idToken, email, refreshToken, and more

Definition of interface AuthResponseData:

export interface AuthResponseData {
  kind: string;
  idToken: string;
  email: string;
  refreshToken: string;
  localId: string;
  expiresIn: string;
  registered?: boolean;
}

Code snippet for the login() method:

login() {

    let authObs: Observable<AuthResponseData>;

    authObs = this.authService.login(this.email, this.password);

    authObs.subscribe(
        resData => {
            console.log('Response Data:', resData);
            this.router.navigateByUrl('/home');
        },
        errRes => {
            console.log('Error Response:', errRes);
        });
}

Implementation of AuthService.login():

login(email: string, password: string) {
    return of(firebase.auth().signInWithEmailAndPassword(email, password)
      .then((user) => {
        console.log('Service User Value', user);
      }).catch((err) => {
        console.log('Service Error', err);
      }));
  }

Seeking guidance on resolving the issue related to assigning the correct type in the Observable. Any suggestions?

angular typescript google-cloud-firestore

Answer 1

Answer №1

One reason I avoid mixing promises and observables is because it's not a hack or workaround.

If you want to convert a promise to an observable, you can do so using RxJS from (RxJS v6.0.0+). According to the documentation:

Creates an Observable from an Array, an array-like object, a Promise, an iterable object, or an Observable-like object.

If a then or a catch method is provided to the promise, then the from operator will return an observable of the promise returned by the corresponding method instead of the source promise. It'd be better to remove them when converting.

Here's an example:

Service

import { from } from 'rxjs';

login(email: string, password: string) {
  return from(firebase.auth().signInWithEmailAndPassword(email, password));
}

Component

login() {
  let authObs: Observable<any>;  // <-- use 'any' instead of a specific type
  authObs = this.authService.login(this.email, this.password);
  authObs.subscribe(
    resData => {
      console.log('Response Data:', resData);
      this.router.navigateByUrl('/home');
    },
    errRes => {
      console.log('Error Response:', errRes);
    }
  );
}

For versions of RxJS prior to v6.0.0, please refer here.

Answer 2

One reason I avoid mixing promises and observables is because it's not a hack or workaround.

If you want to convert a promise to an observable, you can do so using RxJS from (RxJS v6.0.0+). According to the documentation:

Creates an Observable from an Array, an array-like object, a Promise, an iterable object, or an Observable-like object.

If a then or a catch method is provided to the promise, then the from operator will return an observable of the promise returned by the corresponding method instead of the source promise. It'd be better to remove them when converting.

Here's an example:

Service

import { from } from 'rxjs';

login(email: string, password: string) {
  return from(firebase.auth().signInWithEmailAndPassword(email, password));
}

Component

login() {
  let authObs: Observable<any>;  // <-- use 'any' instead of a specific type
  authObs = this.authService.login(this.email, this.password);
  authObs.subscribe(
    resData => {
      console.log('Response Data:', resData);
      this.router.navigateByUrl('/home');
    },
    errRes => {
      console.log('Error Response:', errRes);
    }
  );
}

For versions of RxJS prior to v6.0.0, please refer here.

Answer 3

Answer №2

If you're facing a problem, this solution may help: Converting Promise to Observable

When you call firebase.auth().signInWithEmailAndPassword(email, password), it returns a promise. You can handle the resolved value and any errors by using the .then() and .catch() methods as shown below:

The code snippet provided above demonstrates how to work with promises in Firebase authentication. Remember that if you want to use Observables instead of Promises, you need to convert the Promise to an Observable using the method Observable.fromPromise.

Answer 4

If you're facing a problem, this solution may help: Converting Promise to Observable

When you call firebase.auth().signInWithEmailAndPassword(email, password), it returns a promise. You can handle the resolved value and any errors by using the .then() and .catch() methods as shown below:

The code snippet provided above demonstrates how to work with promises in Firebase authentication. Remember that if you want to use Observables instead of Promises, you need to convert the Promise to an Observable using the method Observable.fromPromise.

Answer 5

Answer №3

It appears that the method you are using to login returns a Promise instead of an Observable, and Promises do not have a subscribe method. To make it work with Observables, you can utilize the from operator. For more information, refer to this question: Convert Promise to Observable

UPDATE:

To convert the response into an Observable rather than an Observable of a Promise, replace of with from. Additionally, remove the catch block. Here is an example of how your code should look like:


// Inside Component
authObs = this.loginService('', '');

authObs.subscribe(
   resData => {
     console.log('Response Data:', resData);

   },
   errRes => {
     console.log('Error Response:', errRes);
   });
}

// Inside Service

public login(email: string, password: string) {
  return from(firebase.auth().signInWithEmailAndPassword(email, password));

}

Answer 6

It appears that the method you are using to login returns a Promise instead of an Observable, and Promises do not have a subscribe method. To make it work with Observables, you can utilize the from operator. For more information, refer to this question: Convert Promise to Observable

UPDATE:

To convert the response into an Observable rather than an Observable of a Promise, replace of with from. Additionally, remove the catch block. Here is an example of how your code should look like:


// Inside Component
authObs = this.loginService('', '');

authObs.subscribe(
   resData => {
     console.log('Response Data:', resData);

   },
   errRes => {
     console.log('Error Response:', errRes);
   });
}

// Inside Service

public login(email: string, password: string) {
  return from(firebase.auth().signInWithEmailAndPassword(email, password));

}

Strategies for dealing with Observable inconsistencies in an Angular application

Answer №1

Answer №2

Answer №3

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