折线未显示-Swift 4

Question

我正在尝试在纽约的一个街区周围绘制一条矩形折线。

这是我的职责。当我运行我的应用程序时，地图会显示在该区域附近，但不会显示彩色线。

func createPolyline(mapView: MKMapView) {
    let point1 = CLLocationCoordinate2DMake(40.785275, -73.969286);
    let point2 = CLLocationCoordinate2DMake(40.782042, -73.971743);
    let point3 = CLLocationCoordinate2DMake(40.783309, -73.974565);
    let point4 = CLLocationCoordinate2DMake(40.786502, -73.972194);
    let point5 = CLLocationCoordinate2DMake(40.785275, -73.969286);

    let points: [CLLocationCoordinate2D]
    points = [point1, point2, point3, point4, point5]

    let geodesic = MKGeodesicPolyline(coordinates: points, count: 5)
    mapView.add(geodesic)

    UIView.animate(withDuration: 1.5, animations: { () -> Void in
        let span = MKCoordinateSpanMake(0.01, 0.01)
        let region1 = MKCoordinateRegion(center: point1, span: span)
        self.mapView.setRegion(region1, animated: true)
    })
}