title: How to force UI "refresh" on nativescript (typescript) with Observables throught http requests?
body: <p>I'm using a TabView component with template syntax to iterate over it and add items inside (using an observable collection and async pipe). My items come from a http request.</p>
  
  <p>My home.component.tns.html as follows:</p>
  
  <pre><code>&lt;ActionBar title="Angular 2 Seed Advanced (nativescript)"&gt;
  &lt;/ActionBar&gt;
  &lt;StackLayout&gt;
    &lt;TabView selectedIndex="0" selectedColor="#FF0000"&gt;
      &lt;template ngFor let-tab [ngForOf]="tabs | async"&gt;
        &lt;StackLayout *tabItem="tab"&gt;
            &lt;Label text="tab item"&gt;&lt;/Label&gt;
        &lt;/StackLayout&gt;
      &lt;/template&gt;
    &lt;/TabView&gt;
  
    &lt;Button text="call something" (tap)="emptymethod()"&gt;&lt;/Button&gt;
  
  &lt;/StackLayout&gt;
  </code></pre>
  
  <p>...and my home.component.ts:</p>
  
  <pre><code>...
      export class HomeComponent{
  
          public tabs: Observable&lt;any[]&gt;;
  
          constructor(private _menuService: MenuService) {
  
              this._menuService.getMenu()
                  .map((menus) =&gt; {
                      let result: Array&lt;any&gt; = [];
  
                      if (menus) {
                          menus.forEach(menu =&gt; {
                              result.push({ 'title': menu.title });
                          });
                      }
                      return result;
                  })
                  .subscribe(
                  data =&gt; {
                      this.tabs = Observable.of&lt;any[]&gt;(data);
                  },
                  error =&gt; error =&gt; this._log.debug(error));
          }
  
          emptymethod() {
              this._log.debug('HomeComponent - nada invoked');
          }
  
          ngOnInit() {
  
          }
      ...
  </code></pre>
  
  <p>When the interface is renderized, the TabView menu does not appears, but when i click over <em>call something</em> button and <em>emptymethod</em> is called the items inside the TabView appears, in other words, after the "refresh" that component appears...</p>
  
  <p>This should not happens automatically?</p>