title: How can I update the subtitle in a delivered NSUserNotification?
body: <p>I'm trying to update the string in the subtitle of a delivered notification (alert), I'm doing it with an <code>NSTimer</code> like this:</p>
  
  <pre><code>[NSTimer scheduledTimerWithTimeInterval:5.0
                                   target:self
                                 selector:@selector(updateSubtitle)
                                 userInfo:nil
                                  repeats:YES];
  
  
  - (void)updateSubtitle
  {
      [[NSUserNotificationCenter defaultUserNotificationCenter].deliveredNotifications 
          enumerateObjectsUsingBlock:^(NSUserNotification *notification, NSUInteger idx, BOOL *stop) {
              notification.subtitle = @"new subtitle";
      }];
  }
  </code></pre>
  
  <p>The code is executing correctly every 5 seconds. But the shown subtitle in the notification alert does not change.</p>
  
  <p>Is there some way to force a "redraw" like <code>setNeedsDisplay</code> or something similar?</p>
  
  <p>Thanks.</p>