Swift MapKit - create a polygon - swift

Question

I am trying to create a polygon on my map to show a boundry. But when I run my app nothing appears. I can see the map but not the polygon What's my error? thanks.
import UIKit
import MapKit
import CoreLocation
class MapScreen : UIViewController {
#IBOutlet var mapView: MKMapView!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
mapView.delegate = self as! MKMapViewDelegate
// center the location on the screen
var location = CLLocationCoordinate2DMake(41.308792, -72.928641)
var span = MKCoordinateSpanMake(0.01, 0.01)
var region = MKCoordinateRegionMake(location, span)
mapView.setRegion(region, animated: true)
//calling the method
addBoundry()
}
func addBoundry(){ //creation of a polygon
var points = [CLLocationCoordinate2DMake(41.311674, -72.925506),
CLLocationCoordinate2DMake(41.307308, -72.928694),
CLLocationCoordinate2DMake(41.307108, -72.928324),
CLLocationCoordinate2DMake(41.307892, -72.930285),
CLLocationCoordinate2DMake(41.307892, -72.931223),
CLLocationCoordinate2DMake(41.307227, -72.932494),
CLLocationCoordinate2DMake(41.308452, -72.931663),
CLLocationCoordinate2DMake(41.308730, -72.932773),
CLLocationCoordinate2DMake(41.308496, -72.931614),
CLLocationCoordinate2DMake(41.308496, -72.931614),
CLLocationCoordinate2DMake(41.311288, -72.931630),
CLLocationCoordinate2DMake(41.311659, -72.930945),
CLLocationCoordinate2DMake(41.312893, -72.932153),
CLLocationCoordinate2DMake(41.313433, -72.930542),
CLLocationCoordinate2DMake(41.313324, -72.929963),
CLLocationCoordinate2DMake(41.312758, -72.929027),
CLLocationCoordinate2DMake(41.312373, -72.927167),
CLLocationCoordinate2DMake(41.311674, -72.925506)]
let polygon = MKPolygon(coordinates: &points, count: points.count)
mapView.add(polygon)
}
func mapView(mapView: MKMapView!, rendererForOverlay overlay: MKOverlay!) -> MKOverlayRenderer! {
if overlay is MKPolygon {
let polygonView = MKPolygonRenderer(overlay: overlay)
polygonView.fillColor = UIColor(red: 0, green: 0.847, blue: 1, alpha: 0.25)
return polygonView
}
return nil
}
}

Answer 1

Your signature for mapView(_:rendererFor:) is incorrect. In Swift 3, it would be:
func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
...
}
If you formally declare your conformance to protocols like MKMapViewDelegate, it will often warn you about these things. For example, best practice would be do so in a class extension rather than in the class definition itself:
extension MapScreen: MKMapViewDelegate {
func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
...
}
}
By the way, if you do that, not only do you get warnings about protocol conformance, but you also don't need to cast it when setting the delegate:
mapView.delegate = self