Draw polygon on MapView using Swift - swift

Question

I have a MKMapView, and a set of coordinates I want to connect with a polygon to draw a rectangle. Below is my code that I have started with.
import UIKit
import MapKit
class mapViewViewController: UIViewController {
#IBOutlet var map: MKMapView!
override func viewDidLoad() {
super.viewDidLoad()
map?.delegate=self
let startingPoint1 = ...
let startingPoint2 = ...
let endingPoint1 = ...
let endingPoint2 = ...
var coordinateInput:[CLLocationCoordinate2D]=[startingPoint1,startingPoint2,endingPoint1,endingPoint2]
let line = MKPolygon(coordinates:&coordinateInput, count:4)
map.addOverlay(line)
}
extension mapViewViewController: MKMapViewDelegate{
func map(_ map: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer{
if overlay is MKPolygon{
let renderer = MKPolygonRenderer(polygon: overlay as! MKPolygon)
renderer.fillColor=UIColor.red.withAlphaComponent(0.5)
renderer.strokeColor=UIColor.orange
renderer.lineWidth=4
return renderer
}
return MKOverlayRenderer()
}
}
The issue I'm running into is that when I launch the map view nothing is displayed on top of the map as expected. I have confirmed all of my coordinates are valid and what I intended them to be, but my current setup is not drawing on the map as I expect. What is the correct way to accomplish this?

Answer 1

Your signature for rendererFor is incorrect. Add a breakpoint or log statement in your method and you will see it is not getting called.
The correct signature is:
func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer { ... }