func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
        if (annotation is MKUserLocation){
            return nil
            }
        else{
            let reuseId = "pin"

            var pinView = mapView.dequeueReusableAnnotationView(withIdentifier: reuseId) as? MKPinAnnotationView

            if pinView == nil {
                pinView = MKPinAnnotationView(annotation: annotation, reuseIdentifier: reuseId)
                pinView!.canShowCallout = false
                pinView!.pinTintColor = .red
                pinView!.animatesDrop = true
                pinView!.rightCalloutAccessoryView = UIButton(type: .detailDisclosure)
            }
            else {
                pinView!.annotation = annotation
            }
                return pinView
        }
    }