formControl.component.ts

export class FormControlComponent {

  myControl = new FormControl();
  results: Observable<any[]>;

  constructor(public http: Http) {
    this.results = this.myControl.valueChanges
      .startWith('someValue')
      .map(text => new formatQuery(text)) // generate a url
      .switchMap(url => this.http.get(url), (_, res)=> res.json());
  }
}