How can I receive updates when an interface changes in Angular?

Question

How can I receive updates when an interface changes in Angular?

I'm attempting to subscribe to my interface and monitor for any changes, but I keep encountering errors.

Fetching data from the API and assigning it to this.candidateProfile :

 export interface CandidateProfile {
 about: string,
 c_id: {},
 certificates_training: [],
 city: string,
 country: string,
 currency: string,
 email: string,
 expectedpayhourly: boolean,
 expectedpayhourlyend: number,
 expectedpayhourlystart: number,
 expectedpaymonthly: {},
 expectedpaymonthlyend: number,
 expectedpaymonthlystart: number,
 experience: [],
 firstname: string,
 hobbies: {},
 jobskills: [],
 langugaes: {},
 lastname: string,
 personalskills: [],
 photo: string,
 remotework: boolean,
 role: string,
 studies: {},
 willingtorelocate: {},
 willingtorelocatecity: {},
 worktype: string
  }

Auth.service.ts :

candidateProfile: Observable<CandidateProfile>;

getProfile(id, token) {
const httpOptions = {
  headers: new HttpHeaders({
    'Content-Type': 'application/json',
    'Authorization': `Bearer ${token}`
  })
};

this.http.get(`users/${id}`, httpOptions).subscribe(data => {
  this.candidateProfile = data;
},
  (error) => { console.log(error) },
  () => {
    console.log('received profile', this.candidateProfile);
  })

 }

Component.ts :

this.auth.candidateProfile.subscribe( data => {
console.log(data)
})

Error message :

this.auth.candidateProfile.subscribe is not a function

angular typescript rxjs

Answer 1

Answer №1

Adjust your authentication service as shown below

export class AuthService {
    private _candidateProfile$: BehaviorSubject<CandidateProfile> = new BehaviorSubject(null);

    getProfile(id, token): void {
        const httpOptions = {
            headers: new HttpHeaders({
                'Content-Type': 'application/json',
                'Authorization': `Bearer ${token}`
            })
        };

        this.http.get(`users/${id}`, httpOptions).subscribe(data => {
                this._candidateProfile$.next(data);
            },
            (error) => { console.log(error) },
            () => {
                console.log('received profile', data);
            })
    }

    get candidateProfile$(): Observable<CandidateProfile> {
      return this._candidateProfile$.asObservable();
    }
}

You can then use it like this:

this.auth.candidateProfile$.subscribe( data => {
console.log(data)
})

Explanation

The objective is to have an internal observable within the service that will broadcast the current candidate profile.

Anywhere in your application, you are able to subscribe to it and receive the latest fetched profile without triggering the getProfile method again (thus avoiding unnecessary AJAX requests).

To make it easier to consume outside of AuthService, a magic getter has been created to abstract it.

get candidateProfile$(): Observable<CandidateProfile> {
  return this._candidateProfile$.asObservable();
}

This converts the BehaviorSubject into a simple Observable. This ensures that consumers of AuthService cannot directly manipulate the Observable.

The only way to update the CandidateProfile is through this specific block of code:

 this.http.get(`users/${id}`, httpOptions).subscribe(data => {
      this._candidateProfile$.next(data);
 });

I also recommend updating your getProfile function as follows

getProfile(id, token): Observable<CandidateProfile> {
    // [...]
    this.http.get(`users/${id}`, httpOptions).subscribe(data => {
           this._candidateProfile$.next(data);
        },
        // [...]
    );

    return this.candidateProfile$;
}

With this modification, you can interact with your class as demonstrated below:

// Fetch new profile.
this.auth.getProfile(id, token).subscribe();
// Retrieve the last requested profile.
this.auth.candidateProfile$.subscribe();

Answer 2

Adjust your authentication service as shown below

export class AuthService {
    private _candidateProfile$: BehaviorSubject<CandidateProfile> = new BehaviorSubject(null);

    getProfile(id, token): void {
        const httpOptions = {
            headers: new HttpHeaders({
                'Content-Type': 'application/json',
                'Authorization': `Bearer ${token}`
            })
        };

        this.http.get(`users/${id}`, httpOptions).subscribe(data => {
                this._candidateProfile$.next(data);
            },
            (error) => { console.log(error) },
            () => {
                console.log('received profile', data);
            })
    }

    get candidateProfile$(): Observable<CandidateProfile> {
      return this._candidateProfile$.asObservable();
    }
}

You can then use it like this:

this.auth.candidateProfile$.subscribe( data => {
console.log(data)
})

Explanation

The objective is to have an internal observable within the service that will broadcast the current candidate profile.

Anywhere in your application, you are able to subscribe to it and receive the latest fetched profile without triggering the getProfile method again (thus avoiding unnecessary AJAX requests).

To make it easier to consume outside of AuthService, a magic getter has been created to abstract it.

get candidateProfile$(): Observable<CandidateProfile> {
  return this._candidateProfile$.asObservable();
}

This converts the BehaviorSubject into a simple Observable. This ensures that consumers of AuthService cannot directly manipulate the Observable.

The only way to update the CandidateProfile is through this specific block of code:

 this.http.get(`users/${id}`, httpOptions).subscribe(data => {
      this._candidateProfile$.next(data);
 });

I also recommend updating your getProfile function as follows

getProfile(id, token): Observable<CandidateProfile> {
    // [...]
    this.http.get(`users/${id}`, httpOptions).subscribe(data => {
           this._candidateProfile$.next(data);
        },
        // [...]
    );

    return this.candidateProfile$;
}

With this modification, you can interact with your class as demonstrated below:

// Fetch new profile.
this.auth.getProfile(id, token).subscribe();
// Retrieve the last requested profile.
this.auth.candidateProfile$.subscribe();

Answer 3

Answer №2

Subscribing to an observable means subscribing to its value, which is not an observable itself. Instead of storing the value directly, store the observable to maintain its functionality:

this.candidateProfile = data;

By storing the observable in 'this.candidateProfile', you ensure that it retains its subscribe function for future use:

this.candidateProfile = this.http.get(`users/${id}`, httpOptions);

I hope this explanation clarifies things for you. Have a great day!

Answer 4

Subscribing to an observable means subscribing to its value, which is not an observable itself. Instead of storing the value directly, store the observable to maintain its functionality:

this.candidateProfile = data;

By storing the observable in 'this.candidateProfile', you ensure that it retains its subscribe function for future use:

this.candidateProfile = this.http.get(`users/${id}`, httpOptions);

I hope this explanation clarifies things for you. Have a great day!

Answer 5

Answer №3

It's important to consider different approaches when handling observables. Rather than returning the observable in your service file, it is recommended to return it directly in your component.

When it comes to error handling, the choice between handling errors in the service or the component is yours. In the example provided below, I have chosen to handle errors in the component.

In your service file, make sure to include the return statement:

getProfile(id, token) {
  const httpOptions = {
    headers: new HttpHeaders({
      'Content-Type': 'application/json',
      'Authorization': `Bearer ${token}`
    })
  };

  return this.http.get(`users/${id}`, httpOptions);
}

In your component.ts file, subscribe to the observable to retrieve the value:

this.auth.candidateProfile.subscribe( data => {
  console.log(data)
}, error => {
  // handle error
});

Answer 6

It's important to consider different approaches when handling observables. Rather than returning the observable in your service file, it is recommended to return it directly in your component.

When it comes to error handling, the choice between handling errors in the service or the component is yours. In the example provided below, I have chosen to handle errors in the component.

In your service file, make sure to include the return statement:

getProfile(id, token) {
  const httpOptions = {
    headers: new HttpHeaders({
      'Content-Type': 'application/json',
      'Authorization': `Bearer ${token}`
    })
  };

  return this.http.get(`users/${id}`, httpOptions);
}

In your component.ts file, subscribe to the observable to retrieve the value:

this.auth.candidateProfile.subscribe( data => {
  console.log(data)
}, error => {
  // handle error
});

How can I receive updates when an interface changes in Angular?

this.auth.candidateProfile.subscribe is not a function

Answer №1

Answer №2

Answer №3

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