adding detail callout accesory view to mkannonationview to show map snapshot

annoation.swift

 func configureDetailView(annotationView: MKAnnotationView) {
   let width = 300
   let height = 200
   
   let snapshotView = UIView()
   let views = ["snapshotView": snapshotView]
   snapshotView.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:[snapshotView(300)]", options: [], metrics: nil, views: views))
   snapshotView.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:[snapshotView(200)]", options: [], metrics: nil, views: views))
   
   self.takeSnapshot(mapView , annotationView: annotationView) { (image, error) in
     let imageview = UIImageView.init(image: image)
     snapshotView.addSubview(imageview)
   }
   
   annotationView.detailCalloutAccessoryView = snapshotView
 }

  
  // Takes a snapshot and calls back with the generated UIImage
 func takeSnapshot(mapView: MKMapView,annotationView: MKAnnotationView, withCallback: (UIImage?, NSError?) -> ()) {
   let options = MKMapSnapshotOptions()
   //options.region = mapView.region
   options.size = mapView.frame.size
   options.mapType = .SatelliteFlyover
   options.scale = UIScreen.mainScreen().scale
   options.camera = MKMapCamera(lookingAtCenterCoordinate: annotationView.annotation!.coordinate, fromDistance: 250, pitch: 65, heading: 0)
   let snapshotter = MKMapSnapshotter(options: options)
   snapshotter.startWithCompletionHandler() { snapshot, error in
     guard snapshot != nil else {
       withCallback(nil, error)
       return
     }
     
     withCallback(snapshot!.image, nil)
   }
 }