Draw polyline with mapkit Swift 3

Question

I want to draw a polyline from the current user location to an annotation point but it doesn't appear to draw anything:

@IBAction func myButtonGo(_ sender: Any) {
    showRouteOnMap()
}

func showRouteOnMap() {
    let request = MKDirectionsRequest()

    request.source = MKMapItem(placemark: MKPlacemark(coordinate: CLLocationCoordinate2D.init(), addressDictionary: nil))
    request.destination = MKMapItem(placemark: MKPlacemark(coordinate: (annotationCoordinatePin?.coordinate)!, addressDictionary: nil))
    request.requestsAlternateRoutes = true
    request.transportType = .automobile

    let directions = MKDirections(request: request)

    directions.calculate { [unowned self] response, error in guard let unwrappedResponse = response else { return }

        if (unwrappedResponse.routes.count > 0) {
            self.mapView.add(unwrappedResponse.routes[0].polyline)
            self.mapView.setVisibleMapRect(unwrappedResponse.routes[0].polyline.boundingMapRect, animated: true)
        }
    }
}

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    let renderer = MKPolylineRenderer(polyline: overlay as! MKPolyline)
    renderer.strokeColor = UIColor.black
    return renderer
}

I tried to run in debug mode and it stops on the break point at line of:

directions.calculate { [unowned self] response, error in guard let unwrappedResponse = response else { return }

What is the cause of this error?

Draw polyline with mapkit Swift 3

1 Answers