Exploring the incorporation of behavior subjects in Angular 8 via services

Question

Exploring the incorporation of behavior subjects in Angular 8 via services

Just getting started with Angular and running into an issue here.

I'm working on an application with multiple sibling components. Whenever I update a value in one component, the changes aren't reflected in the other components. I've heard that using Behaviour Subject can solve this problem. But how exactly do I go about implementing it in my service, components, and templates?

Here's a snippet of my code:

----------------------Service File---------------------------

//import


@Injectable() 
export class CoachService {

    apiURL = environment.apiURL;

    constructor(private http: HttpClient ) { }

    coachProfile(token :string)
    {  
    return this.http.post<any>(this.apiURL+'/coach/profile_infos',{
      token: token
      })        
    }

    updateProfile(info: any, token: string, us_id: string) {
      return this.http.post<any[]>(this.apiURL + '/coach/update_profile', {
        token: token,
        us_id: us_id,
        us_lang: info.us_lang,
        us_firstname: info.us_firstname,
        us_lastname: info.us_lastname,
        us_sex: info.us_sex,
        us_birthdate: info.us_birthdate,
        us_national_number : info.us_national_number,
        us_email: info.us_email,
        us_gsm: info.us_gsm,        
        online_profile: info.online_profile,          
        us_address: info.us_address,
        us_zip: info.us_zip,
        us_city: info.us_city,
        country:{
          id: info.country.id
        }
        })

    } 

}

----------Component.ts File-------------------

//import
//component decorator

export class CoordonneesComponent implements OnInit, OnDestroy {

private coachProfile;
  token: string = localStorage.getItem('token');
  us_id : string;
  us_lang: string; 
  infos_profile: any;
  online: any;


  constructor(private translate: TranslateService,private coachService: CoachService, private router: Router) { }

  ngOnInit() {

    this.coachProfile=this.coachService.coachProfile(this.token)
      .subscribe((data) => {
        this.infos_profile = data.results;
        this.online = this.infos_profile.online_profile;
        this.translate.use(this.infos_profile.us_lang)
        this.infos_profile.lang= this.infos_profile.us_lang;

      });

   .....
  }


updateCoordonees() {
  this.coachService.updateProfile(this.infos_profile, this.token, this.us_id)
    .subscribe((data: any) => {

      if(data.success && data.msg!=null)
      { 
  // do something
      }
      else
      {
       // do something
      }

    },
      (err) => {
        // do something
      });

}  



  ngOnDestroy() {
    this.countrieList.unsubscribe();
    this.coachProfile.unsubscribe();  
  }


}

angular typescript httpclient angular8 behaviorsubject

Answer 1

Answer №1

If you're looking for a straightforward approach, here's a simple way to achieve it:

@Injectable() 
export class ProfileService {

    private profileObs$: BehaviorSubject<Profile> = new BehaviorSubject(null);

    getProfileObs(): Observable<Profile> {
        return this.profileObs$.asObservable();
    }

    setProfileObs(profile: Profile) {
        this.profileObs$.next(profile);
    }
}

With this setup, any updates made within the application can be reflected by using ProfileService, ensuring that all subscribers receive the updated information. It is advisable to subscribe in the ngOnInit method.

ngOnInit() {
  this.profileService.getProfileObs().subscribe(profile => this.profile = profile);
}

Remember to always unsubscribe from observables to prevent memory leaks!

There are numerous ways to accomplish this - one method is to use a subscription and unsubscribe in ngOnDestroy(), or utilize another subject and deliver it to takeUntil as shown below:

unsubscribe$: Subject<boolean> = new Subject();

...

ngOnInit() {    
  this.profileService.getProfileObs()
                     .pipe(takeUntil(this.unsubscribe$))
                     .subscribe(profile => this.profile = profile);
}

ngOnDestroy() {
  this.unsubscribe$.next(true);
  this.unsubscribe$.complete();
}

Answer 2

If you're looking for a straightforward approach, here's a simple way to achieve it:

@Injectable() 
export class ProfileService {

    private profileObs$: BehaviorSubject<Profile> = new BehaviorSubject(null);

    getProfileObs(): Observable<Profile> {
        return this.profileObs$.asObservable();
    }

    setProfileObs(profile: Profile) {
        this.profileObs$.next(profile);
    }
}

With this setup, any updates made within the application can be reflected by using ProfileService, ensuring that all subscribers receive the updated information. It is advisable to subscribe in the ngOnInit method.

ngOnInit() {
  this.profileService.getProfileObs().subscribe(profile => this.profile = profile);
}

Remember to always unsubscribe from observables to prevent memory leaks!

There are numerous ways to accomplish this - one method is to use a subscription and unsubscribe in ngOnDestroy(), or utilize another subject and deliver it to takeUntil as shown below:

unsubscribe$: Subject<boolean> = new Subject();

...

ngOnInit() {    
  this.profileService.getProfileObs()
                     .pipe(takeUntil(this.unsubscribe$))
                     .subscribe(profile => this.profile = profile);
}

ngOnDestroy() {
  this.unsubscribe$.next(true);
  this.unsubscribe$.complete();
}

Answer 3

Answer №2

To start, create a new BehaviorSubject

this._source = new BehaviorSubject<yourType>(initialValue);
this.source = this._source.asObservable();

Next, define a function to update the BehaviorSubject's value

updateSource(newValue) {
    this._source.next(newValue)
}

Now, in your components, subscribe to the source

this.service.source.subscribe();

Remember that a BehaviorSubject always requires an initial value and emits the last one

For more information, see the documentation: https://www.learnrxjs.io/subjects/behaviorsubject.html

If you need to share data from an HTTP request, consider using the shareReplay() operator instead. This allows multiple components to subscribe to the request without making duplicate requests.

Check out the documentation for more details: https://www.learnrxjs.io/operators/multicasting/sharereplay.html

Answer 4

To start, create a new BehaviorSubject

this._source = new BehaviorSubject<yourType>(initialValue);
this.source = this._source.asObservable();

Next, define a function to update the BehaviorSubject's value

updateSource(newValue) {
    this._source.next(newValue)
}

Now, in your components, subscribe to the source

this.service.source.subscribe();

Remember that a BehaviorSubject always requires an initial value and emits the last one

For more information, see the documentation: https://www.learnrxjs.io/subjects/behaviorsubject.html

If you need to share data from an HTTP request, consider using the shareReplay() operator instead. This allows multiple components to subscribe to the request without making duplicate requests.

Check out the documentation for more details: https://www.learnrxjs.io/operators/multicasting/sharereplay.html

Answer 5

Answer №3

There are various methods to achieve this task. One approach is outlined below.

1) Implement your service as follows:

// ReplaySubject provides more flexibility than BehaviorSubject, allowing you 
// to specify the number of past emissions to retain. You can replicate this
// behavior using BehaviorSubject by following this code snippet:
// private _coachProfile$: BehaviorSubject<any | null> = 
//    new BehaviorSubject<any | null>(null);
private _coachProfile$: ReplaySubject<any> = new ReplaySubject<any>(1);

coachProfile(token :string)
{  
  return this.http.post<any>(this.apiURL+'/coach/profile_infos',{
    token: token,
  }).subscribe((profile) => this._coachProfile$.next(profile));        
}

subscribeToGetCoachProfile$()
{  
  return this._coachProfile$.asObservable();       
}

2) Usage in your components:

ngOnInit() {
  this.coachService.subscribeToGetCoachProfile$()
    .subscribe((profile) => this.coachProfile = profile);
}

While there are other possible approaches to consider, I find this method to be the most straightforward based on the provided code snippet in your question.

Additionally, you may find related discussions on stackoverflow addressing similar queries. Take a look at this alternative approach for further insights: Multiple subscriptions without recalculate common part

Answer 6

There are various methods to achieve this task. One approach is outlined below.

1) Implement your service as follows:

// ReplaySubject provides more flexibility than BehaviorSubject, allowing you 
// to specify the number of past emissions to retain. You can replicate this
// behavior using BehaviorSubject by following this code snippet:
// private _coachProfile$: BehaviorSubject<any | null> = 
//    new BehaviorSubject<any | null>(null);
private _coachProfile$: ReplaySubject<any> = new ReplaySubject<any>(1);

coachProfile(token :string)
{  
  return this.http.post<any>(this.apiURL+'/coach/profile_infos',{
    token: token,
  }).subscribe((profile) => this._coachProfile$.next(profile));        
}

subscribeToGetCoachProfile$()
{  
  return this._coachProfile$.asObservable();       
}

2) Usage in your components:

ngOnInit() {
  this.coachService.subscribeToGetCoachProfile$()
    .subscribe((profile) => this.coachProfile = profile);
}

While there are other possible approaches to consider, I find this method to be the most straightforward based on the provided code snippet in your question.

Additionally, you may find related discussions on stackoverflow addressing similar queries. Take a look at this alternative approach for further insights: Multiple subscriptions without recalculate common part

Answer 7

Answer №4

Here is a solution using a behavior subject to address your issue:

@Injectable()
export class CoachService {
  apiURL = environment.apiURL;

  constructor(private http: HttpClient) { }

  updateProfile(info, token, us_id): Observable<any> {
    return Observable.create((behaviorSubject: BehaviorSubject<any>) => {
      const requestData = {
        token: token,
        us_id: us_id,
        us_lang: info.us_lang,
        us_firstname: info.us_firstname,
        us_lastname: info.us_lastname,
        us_sex: info.us_sex,
        us_birthdate: info.us_birthdate,
        us_national_number: info.us_national_number,
        us_email: info.us_email,
        us_gsm: info.us_gsm,
        online_profile: info.online_profile,
        us_address: info.us_address,
        us_zip: info.us_zip,
        us_city: info.us_city,
        country: {
          id: info.country.id
        }
      };
      const url = [this.apiURL, '/coach/update_profile'].join('');

      return this.http.post(url, requestData).subscribe(
        data => {
          behaviorSubject.next(data);
        },
        err => {
          behaviorSubject.error(err);
          if (err && err.status === 401) {
            // Implement error handling here
          }
        }
      );
    });
  }

}

To post data and subscribe to the result of the Behavior Subject in your component, simply use the following method:

 updateCoordonees() {
  this.coachService.updateProfile(this.infos_profile, this.token, this.us_id)
    .subscribe((data: any) => {

      if (data.success && data.msg != null) {
        // Perform actions on success
      }

    },
      (err) => {
        // Handle errors here
      });
}

Answer 8

Here is a solution using a behavior subject to address your issue:

@Injectable()
export class CoachService {
  apiURL = environment.apiURL;

  constructor(private http: HttpClient) { }

  updateProfile(info, token, us_id): Observable<any> {
    return Observable.create((behaviorSubject: BehaviorSubject<any>) => {
      const requestData = {
        token: token,
        us_id: us_id,
        us_lang: info.us_lang,
        us_firstname: info.us_firstname,
        us_lastname: info.us_lastname,
        us_sex: info.us_sex,
        us_birthdate: info.us_birthdate,
        us_national_number: info.us_national_number,
        us_email: info.us_email,
        us_gsm: info.us_gsm,
        online_profile: info.online_profile,
        us_address: info.us_address,
        us_zip: info.us_zip,
        us_city: info.us_city,
        country: {
          id: info.country.id
        }
      };
      const url = [this.apiURL, '/coach/update_profile'].join('');

      return this.http.post(url, requestData).subscribe(
        data => {
          behaviorSubject.next(data);
        },
        err => {
          behaviorSubject.error(err);
          if (err && err.status === 401) {
            // Implement error handling here
          }
        }
      );
    });
  }

}

To post data and subscribe to the result of the Behavior Subject in your component, simply use the following method:

 updateCoordonees() {
  this.coachService.updateProfile(this.infos_profile, this.token, this.us_id)
    .subscribe((data: any) => {

      if (data.success && data.msg != null) {
        // Perform actions on success
      }

    },
      (err) => {
        // Handle errors here
      });
}

Exploring the incorporation of behavior subjects in Angular 8 via services

Answer №1

Answer №2

Answer №3

1) Implement your service as follows:

2) Usage in your components:

Answer №4

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