Swift - Google Map crashes with 'unexpectedly found nil' error - ios

Question

I am trying to set a GoogleMap to a UIView and add it as a Subview. However, when running the app I get this error:
fatal error: unexpectedly found nil while unwrapping an Optional value
It crashes at code line:
mapView.camera = camera
Here's my full ViewController code:
class LocationViewController: UIViewController {
#IBOutlet weak var mapView: GMSMapView!
override func viewDidLoad() {
super.viewDidLoad()
let camera = GMSCameraPosition.camera(withLatitude: 15.4989, longitude: 73.8278, zoom: 6)
mapView.camera = camera
mapView = GMSMapView.map(withFrame: CGRect.zero, camera: camera)
mapView.isMyLocationEnabled = true
mapView.settings.myLocationButton = true
self.view.addSubview(self.mapView)
}
}
I went through a few other similar SO threads and all of them have the same code. In my case the UI freezes and crashes with this error. What am I doing wrong?
EDIT
Yes, I have set the UIView's custom class as GMSMapView

Answer 1

Could you please use below code and try:
override func viewDidLoad() {
super.viewDidLoad()
let camera = GMSCameraPosition.camera(withLatitude: 15.4989, longitude: 73.8278, zoom: 6)
mapView.camera = camera
mapView.isMyLocationEnabled = true
mapView.settings.myLocationButton = true
self.view.addSubview(self.mapView)
}

Answer 2

you have to do it like this
you have to give frame to GMSMapview
Here in this line self.view.bounds , you have to set your custom view
let camera = GMSCameraPosition.camera(withLatitude: 15.4989,
longitude: 73.8278,
zoom: 6)
let mapView = GMSMapView.map(withFrame: self.view.bounds, camera: camera)

Answer 3

This is the syntax in swift 3.0
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation])
{
print(locations)
mapview.delegate = self
currentLocation = CLLocationCoordinate2D(latitude:CLLocationDegrees(locations[0].coordinate.latitude), longitude:CLLocationDegrees(locations[0].coordinate.longitude))
mapview.camera = GMSCameraPosition.camera(withTarget:locations[0].coordinate, zoom: 10.0)
mapview.isMyLocationEnabled = true
}