@Injectable()
export class ApiService {
    public serviceName: string = "";
    urlRoot: string = "http://localhost:3000/api/v1/";

    constructor(private http: Http){
    }

    get(urlApi?: string, params?: Array<object>): Observable<any>{
        return this.http.get(this.urlRoot+this.serviceName, {headers: this.getHeaders()})
                        .map((res:Response) => res.json())
    }

@Injectable()
export class NewsService extends ApiService{
    public serviceName: string = "news";
    private id: string;

}

export class NewsComponent implements OnInit {
  private news: News[];

  constructor(private newsService: NewsService) { }

  ngOnInit() {
    this.newsService.get().subscribe(
      result => this.news = result,
      error => console.log("Error: ", error)
    );
  }