drop pin with long touch in google maps
<p>i can't add marker with long touch in google maps in swift 
i have try lots of codes but it doesn't work for me
what should i do !?</p>

<pre><code>override func viewDidLoad() {

    super.viewDidLoad()        
    GMSServices.provideAPIKey("AIzaSyBw95wEhcSiSBmPWuYkiK0_IBnZQK-Lm7I")


    locationManager.delegate = self
    locationManager.requestWhenInUseAuthorization()
    locationManager.desiredAccuracy = kCLLocationAccuracyBest
    locationManager.startUpdatingLocation()
}

func locationManager(manager: CLLocationManager, didFailWithError error: NSError) {
    print("Error" + error.description)
}

func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    let userLocation = locations.last
    let center = CLLocationCoordinate2D(latitude: userLocation!.coordinate.latitude, longitude: userLocation!.coordinate.longitude)

    let camera = GMSCameraPosition.cameraWithLatitude(userLocation!.coordinate.latitude,
                                                      longitude: userLocation!.coordinate.longitude, zoom: 16)
    let mapView = GMSMapView.mapWithFrame(CGRectZero, camera: camera)
    mapView.myLocationEnabled = true
    mapView.settings.myLocationButton = true
    view = mapView

   let  position = CLLocationCoordinate2DMake(10, 10)
    let marker = GMSMarker(position: position)


    marker.opacity = 0.6
    marker.position = center
    marker.title = "Current Location"
    marker.snippet = ""
    marker.map = mapView
    //mapView.clear()
}
</code></pre>

<p>Ant help would be appreciate  </p>