Draw polyline using Swift

Question

I'm trying to get an understanding of how to draw polylines using Swift. I've looked at the documentation, referenced some tutorials, and checked out some other SO posts, but I still can't get the thing to draw a line on my map. Here's my code. Anyone tell me what I'm doing wrong here?

import UIKit
import MapKit

class FirstViewController: UIViewController {

    @IBOutlet weak var map: MKMapView!

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)

        let location = CLLocationCoordinate2D(
            latitude: -73.761105,
            longitude: 41.017791
        )

        let span = MKCoordinateSpanMake(0.07, 0.07)
        let region = MKCoordinateRegion(center: location, span: span)
        map.setRegion(region, animated: true)

        let annotation = MKPointAnnotation()
        annotation.setCoordinate(location)
        annotation.title = "White Plains"
        annotation.subtitle = "Westchester County"
        map.addAnnotation(annotation)

        var locations = [CLLocation(latitude: -73.761105, longitude: 41.017791), CLLocation(latitude: -73.760701,longitude: 41.019348), CLLocation(latitude: -73.757201, longitude: 41.019267), CLLocation(latitude: -73.757482, longitude: 41.016375), CLLocation(latitude: -73.761105, longitude: 41.017791)]
        var coordinates = locations.map({(location: CLLocation!) -> CLLocationCoordinate2D in return location.coordinate})
        var polyline = MKPolyline(coordinates: &coordinates, count: locations.count)

        self.map.addOverlay(polyline)

    }

    func mapView(mapView: MKMapView!, rendererForOverlay overlay: MKOverlay!) -> MKOverlayRenderer! {
        if overlay is MKPolyline {
            var polylineRenderer = MKPolylineRenderer(overlay: overlay)
            polylineRenderer.strokeColor = UIColor.blueColor()
            polylineRenderer.lineWidth = 5
            return polylineRenderer
        }

        return nil
    }

}

Thanks!

Answer 1

Here MKGeodesicPolyline will solve your problem. Add object of MKGeodesicPolyline instead of MKPolyline.

In your code remove below two lines:

    let polyline = MKPolyline(coordinates: &coordinates, count: locations.count)
    map.add(polyline)

And add these lines:

    let geodesic = MKGeodesicPolyline(coordinates: coordinates, count: 2)
    map.addOverlay(geodesic)

Swift 5.0:

func createPolyline(mapView: MKMapView) {
    let point1 = CLLocationCoordinate2DMake(-73.761105, 41.017791);
    let point2 = CLLocationCoordinate2DMake(-73.760701, 41.019348);
    let point3 = CLLocationCoordinate2DMake(-73.757201, 41.019267);
    let point4 = CLLocationCoordinate2DMake(-73.757482, 41.016375);
    let point5 = CLLocationCoordinate2DMake(-73.761105, 41.017791);
    
    let points: [CLLocationCoordinate2D]
    points = [point1, point2, point3, point4, point5]
    
    let geodesic = MKGeodesicPolyline(coordinates: points, count: 5)
    map.addOverlay(geodesic)
    
    UIView.animate(withDuration: 1.5, animations: { () -> Void in
        let span = MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01)
        let region1 = MKCoordinateRegion(center: point1, span: span)
        self.map.setRegion(region1, animated: true)
    })
}

Objective C code:

- (void) createGeoPolyline {
    
    CLLocationCoordinate2D point1 = { -73.761105, 41.017791 };
    CLLocationCoordinate2D point2 = { -73.760701, 41.019348 };
    CLLocationCoordinate2D point3 = { -73.757201, 41.019267 };
    CLLocationCoordinate2D point4 = { -73.757482, 41.016375 };
    CLLocationCoordinate2D point5 = { -73.761105, 41.017791 };

   CLLocationCoordinate2D points[] = {point1, point2, point3, point4, point5};
    
    MKGeodesicPolyline *geodesic = [MKGeodesicPolyline polylineWithCoordinates:&points[0] count:5];
    [self.mapView addOverlay:geodesic];
    
    [UIView animateWithDuration:1.5 animations:^{
        MKCoordinateRegion region;
        region.center = point1;
        
        MKCoordinateSpan span;
        span.latitudeDelta  = 0.01;
        span.longitudeDelta = 0.01;
        region.span = span;
        [self.mapView setRegion:region animated:YES];
    }];
}

Above Objective C code works perfect and it will show overlay below:

But if you try Swift code it will not. I tried as much as I can to solve it out but It won't change. May be it is bug from MapKit framework.