getCatalogs(): Observable<Catalog[]> {
    const api_path = this.dataUrl + `metadata/getcatalogs/name/?user=${this.user.username}&password=${this.user.password}`;
    return this.http.get<Catalog[]>(api_path);
  }

onSelect(user: User): void {
    this.selectedUser = user;
    this.datasourceService.user = user; // sets the user, as i can't figure out how to send it as a parameter, and subscribe to that call
    this.datasourceService.getCatalogs() // had to run this here so that the Observable would have at least one subscription to make it run.
      .subscribe(catalogs => {this.catalogs = catalogs; });
  }

@Input() user: User;
  public catalogs$: Observable<Catalog[]>;
  constructor(private datasourceService: DatasourceService) { }

  ngOnInit() {
    this.catalogs$ = this.datasourceService.getCatalogs();
    this.datasourceService.getCatalogs()
      .subscribe(catalogs => {this.catalogs = catalogs; });
  }

<div *ngIf="user">

  <h3>Catalogs for User: {{user.username}}</h3>


    <ul >
      <li  *ngFor="let catalog of catalogs$ | async">
        {{ catalog.name }}
      </li>
    </ul>

</div>

providers: [DatasourceService],