// app.component.html <div *ngIf="productSuppliers$ | async as suppliers"> <div *ngFor="let supplier of suppliers"> {{ supplier.name }} </div> </div> // app.component.ts productSuppliers$ = this.productService.productSuppliers$; // product.service.ts selectedProduct$ = ... productSuppliers$ = this.selectedProduct$.pipe( switchMap(product => forkJoin( product.supplierIds.map( supplierId => this.http.get<Supplier>(`${url}/${supplierId}`)) ) );