Am I missing something? we are injecting service here as: export class AppComponent implements OnInit, OnDestroy { . . . constructor(**private** accountService: AccountService, . . .) { } and then we are using it in app component's html: <span class="nav-link"><span class="nav-text">Cash: {{**accountService.balance** | currency:'USD':'symbol':'.2'}}</span></span> I getting error that it can't be use as private....