import { Component } from '@angular/core' ; import { Observable } from 'rxjs/Observable' ; import { DataService } from './core' ; @ Component ( { selector : 'ro-root' , templateUrl : './app.component.html' , styleUrls : [ './app.component.scss' ] } ) export class AppComponent { isFetching : Observable < boolean > ; constructor ( dataService ) { this . isFetching = dataService . isFetching ; } }