title: Bind Observable to template using async
body: <p>I'm trying to bind an Observable to a template variable in Angular by doing:</p>
  
  <pre><code>[class.active]="isBookmarked$ | async"
  </code></pre>
  
  <p>In the ngOnInit, I'm setting the Observable:</p>
  
  <pre><code>var promise = this.cacheService.getItem(this.bookmarkId).then(() =&gt; {
      return true;
  }).then(() =&gt; {
      return false;
  });
  this.isBookmarked$ = Observable.fromPromise(promise);
  </code></pre>
  
  <p>Which works fine when I load the page. But when I add or remove an item, the template does not recognize the change detection.</p>
  
  <pre><code>this.cacheService.removeItem(this.bookmarkId).then(() =&gt; { });
  // or
  this.cacheService.saveItem(this.bookmarkId, true, "bookmarks").then(() =&gt; { });
  </code></pre>
  
  <p>I've tried different Observables and also tried a Promise without making it an Observable, but I can't get it to work.</p>