I have completed Project16 by following the instructions as far as I can tell, but in the end it isn't showing the map pins at all anymore.

When I add this function as instructed here, it causes the map pins to stop showing. But if I delete or comment out this function then it shows the map pins, just without annotation information available.

func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
        guard annotation is Capital else { return nil }
        let identifier = "Capital"
        var annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: identifier)        

        if annotationView == nil {
            annotationView = MKAnnotationView(annotation: annotation, reuseIdentifier: identifier)
            annotationView?.canShowCallout = true

            let btn = UIButton(type: .detailDisclosure)
            annotationView?.rightCalloutAccessoryView = btn
        } else {
            annotationView?.annotation = annotation
        }

        return annotationView
}

I've looked over this function a few times now and can't seem to find any differences between this and what Paul gave us in the instructions. Does anybody know how to make this work?

And yes, I have made my ViewController the Delegate for the MKMapView and made it conform to MKMapViewDelegate as instructed.