title: UIAlertController not appearing at all
body: <p>I am trying to add an <code>UIAlertController</code> to my app but it's not appearing at all. I have tried the following:</p>
  
  <pre><code>UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Message" message:@"Web Service is not available." preferredStyle:UIAlertControllerStyleAlert];
  
  UIAlertAction* ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:nil];
  [alertController addAction:ok];
  
  [self presentViewController:alertController animated:YES completion:nil];
  </code></pre>
  
  <p>but this does not appear at all, what am I doing wrong?</p>