title: How to async pipe an observable in Angular
body: <p>I have a service that has some asynchronous stuff to do, how can I postpone a data binding render until the service has done its asynchronous work?</p>
  
  <pre><code>this.sessionService.onSessionChange().subscribe(function(session) {
      console.log(session);
      self.user = session.user;
  });
  </code></pre>
  
  <p>Service:</p>
  
  <pre><code>onSessionChange(): Observable&lt;Session&gt; {
      return this.sessionObservable.asObservable();
  }
  </code></pre>
  
  <p>The user is undefined because the session isn't ready yet:</p>
  
  <pre><code>&lt;h4&gt;Hi {{user.name}}.&lt;/h4&gt;
  </code></pre>
  
  <p>How can I use a pipe with my onSessionChange observable?</p>