title: *ngFor output filtering by pipes
body: <p>I have a HTML construction like:</p>
  
  <pre><code>&lt;div *ngFor="#notification of notifications"
        [innerHTML]="notification | notificationHTML"&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>And a <code>notificationHTML</code> pipe:</p>
  
  <pre><code>transform(notification: string, args: any[]): any {
  var example: any;
  this._service.GetExample(notification)
       .subscribe(e =&gt; {
           example = e;
        });
  return "&lt;span&gt;" + example + "&lt;/span&gt;";
  }
  </code></pre>
  
  <p>The problem is that <code>example</code> variable is equal to <code>undefined</code>, because function <code>GetExample</code> does not have time to execute on time. How can I solve this?</p>