errorHandle angular 7

How to manage error block in this situation - error managing in service and send to component

Here storing data in BehaviorSubject in the first load and subscribing data from where I need.

just initializing preload function from app.component when the app runs - but I want to know here if its an error

//**app component**
//just initializing preload function() when the app runs - but I want to know here if its an error
ngOnInit() {
    this.projectsService.preloadAllProjects();
}




// == services ==

//preload all projects
  preloadAllProjects(){
    this.http.get('/api/project/allprojects').pipe( map( response => response )).subscribe(result => {
      this.allProjectsBehavior.next(result);
    });
  };

If you want to follow the subject path:

//**app component**
//just initializing preload function() when the app runs - but I want to know here if its an error
ngOnInit() {
    this.projectsService.preloadAllProjects();
    this.projectService.error$.subscribe(error => console.log(error));
}




// == services ==

//preload all projects
  error$: Subject<string> = new Subject();
  preloadAllProjects(){
    this.http.get('/api/project/allprojects').pipe( map( response => response )).subscribe(result => {
      this.allProjectsBehavior.next(result);
    }, error => this.error$.next(error);
  };

or you can basically return an Observable from preloadAllProjects:

//**app component**
//just initializing preload function() when the app runs - but I want to know here if its an error
ngOnInit() {
    this.projectsService.preloadAllProjects().subscribe(success => {}, error => console.log(error))
}




// == services ==

//preload all projects
  error$: Subject<string> = new Subject();
  preloadAllProjects(){
    return new Observable(observer => {
    this.http.get('/api/project/allprojects').pipe( map( response => response )).subscribe(result => {
      this.allProjectsBehavior.next(result);
      observer.next(true);
      observer.complete();
    }, error => observer.error(error);
   });
  };