谷歌地图多边形线不显示在迅速5

Question

我正在快速5中使用Google地图。但是多边形线不显示多边形线。 这是我的viewcontroller代码。

 class ViewController: UIViewController {
  @IBOutlet weak var googleMap: GMSMapView!

 override func viewDidLoad() {
    super.viewDidLoad()
    tempPolygons()
 }

func tempPolygons(){
    let polygon = GMSPolygon()
    let rect = GMSMutablePath()
    rect.add(CLLocationCoordinate2DMake(18.546160, 73.903992))
    rect.add(CLLocationCoordinate2DMake(18.546099, 73.904817))
    rect.add(CLLocationCoordinate2DMake(18.545922, 73.905643))
    rect.add(CLLocationCoordinate2DMake(18.545854, 73.905973))
    rect.add(CLLocationCoordinate2DMake(18.545105, 73.905915))
    rect.add(CLLocationCoordinate2DMake(18.543153, 73.904867))
    rect.add(CLLocationCoordinate2DMake(18.543016, 73.903805))
    rect.add(CLLocationCoordinate2DMake(18.545473, 73.903863))
    rect.add(CLLocationCoordinate2DMake(18.546140, 73.904013))

    polygon.path = rect
  //  polygon.fillColor =
    //polygon.strokeColor = UIColor.black
    polyline.strokeColor = .black
    polygon.strokeWidth = 1
    polygon.map = googleMap
  }

}

请帮我