title: How do you check if an MKAnnotation is available within a MKCoordinateRegion
body: <p>I've noticed that if I use MKMapView's <code>selectAnnotation:animated:</code>, that it will scroll my map off screen if the MKAnnotation is not displayed in the current MKCoordinateRegion that my map is displaying.</p>
  
  <p>Is there a trivial way to check if an annotation is currently on screen within the specified MKCoordinateRegion? I'd like to be able to select an annotation that's only on screen and not something offscreen. </p>