问angular4订阅web服务

EN

public value = '';
public dataSource: Observable<any>;
public subs: Subscription;

constructor(private searchService: SearchService) { }

ngOnInit() {
  this.dataSource = Observable
    .create((observer: Observer<any>) => {
      observer.next(this.value);
      observer.complete();
    })
    .mergeMap((token: string) => this.searchService.getSearch(this.value));
  this.subs = this.dataSource.subscribe(x => console.log(x));
}

<md-input-container class="w-75">
  <input mdInput [(ngModel)]="value"
    [typeahead]="dataSource"
    (typeaheadLoading)="changeTypeaheadLoading($event)"
    (typeaheadNoResults)="changeTypeaheadNoResults($event)"
    (typeaheadOnSelect)="typeaheadOnSelect($event)"
    typeaheadOptionsLimit="10"
    typeaheadOptionField="title"
    typeaheadWaitMs="250"
    typeaheadMinLength="3"
    [typeaheadItemTemplate]="customItemTemplate"
    placeholder="Entrez votre recherche ici">
  <span *ngIf="typeaheadLoading===true"><i class="fa fa-circle-o-notch fa-spin fa-fw"></i></span>
  <div *ngIf="typeaheadNoResults===true">
    <i class="fa fa-times-circle-o" aria-hidden="true"></i> Aucun résultat.
  </div>
  <md-hint align="end">rechercher dans la sphère éducative</md-hint>
</md-input-container>
<button type="submit" [routerLink]="resultUrl()" md-mini-fab><i class="fa fa-search"></i></button>