Annotation details after detail disclosure pressed?

You might have an easier time using the MKMapViewDelegate mapView:annotationView:calloutAccessoryControlTapped: method, which tells you directly which annotation view was tapped.

A reliable way (if you must use a custom method) is to look at the map view's selectedAnnotations property.

Though the property is an NSArray, since the map view only allows one annotation to be selected at a time, the one that the user just tapped will be at index 0 so it would be:

id<MKAnnotation> annTapped = [mapView.selectedAnnotations objectAtIndex:0];

//Here, you can cast annTapped to a custom annotation class if needed.
//Be sure to check what kind of class it is first.

You may also want to first check that mapView.selectedAnnotations.count is not zero just to be safe.

However, a better way (as nevan king already answered) than using addTarget and a custom action method is to use the map view's calloutAccessoryControlTapped delegate method where the annotation is directly accessible through the view parameter using:

id<MKAnnotation> annTapped = view.annotation;