title: annotationView delegate and MKAnnotation
body: <p>So I have create a class X as follows:</p>
  
  <pre><code>@interface X : NSObject &lt;MKAnnotation&gt; {
      CLLocationCoordinate2D  coordinate;
      NSString * title;
      NSString * subtitle;
      UIImage * image;
      NSInteger * tag;
  }
  
  @property (nonatomic, readonly) CLLocationCoordinate2D  coordinate;
  @property (nonatomic, retain) NSString * title;
  @property (nonatomic, retain) NSString * subtitle;
  @property (nonatomic, retain) UIImage * image;
  @property (nonatomic, readwrite) NSInteger * tag;
  
  @end
  </code></pre>
  
  <p>Inside the:</p>
  
  <ul>
  <li>(void) mapView: (MKMapView *) mapView annotationView:(MKAnnotationView *) view calloutAccessoryControlTapped:(UIControl *) control</li>
  </ul>
  
  <p>I would like to be able to access the tag property that X has. How is this possible?
  Can I do [control tag]? How is this suppose to work?</p>