如何绘制不在道路上的路线，MKMapView

let mapView = MKMapView()
mapView.delegate = self

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    if overlay is MKPolyline {
        let renderer = MKPolylineRenderer(overlay: overlay)
        renderer.strokeColor = UIColor.red
        renderer.lineWidth = 3
        return renderer
    }
    return MKOverlayRenderer(overlay: overlay)
}

let coordinates = [
    CLLocationCoordinate2D(latitude: 37.7749, longitude: -122.4194),
    CLLocationCoordinate2D(latitude: 37.3352, longitude: -121.8811),
    // 添加更多坐标点...
]
let polyline = MKPolyline(coordinates: coordinates, count: coordinates.count)

mapView.addOverlay(polyline)