Swift 3 - store the User Location and call it from different View Controllers

Question

I'm pretty new in programming and this is my first app, so sorry if the approach is very shabby.

I created a helper method to get the user location, because I need to call it from different view controllers so I thought this was a cleaner way to do it. But I don't know why is not working now (no errors, it just show the general view of Europe). But when it was inside the view controller it worked perfectly fine.

I got this new approach from the course I'm doing and I've been researching in many sources. I've also checked this question but I didn't find any solution yet.

Here is the method I created in the GMSClient file. It will get the user location, but if the user disables this option, it will show the default position (centred in Berlin):

    extension GMSClient: CLLocationManagerDelegate {

    //MARK: Initial Location: Berlin

    func setDefaultInitialLocation(_ map: GMSMapView) {
        let camera = GMSCameraPosition.camera(withLatitude: 52.520736, longitude: 13.409423, zoom: 8)
        map.camera = camera

        let initialLocation = CLLocationCoordinate2DMake(52.520736, 13.409423)
        let marker = GMSMarker(position: initialLocation)
        marker.title = "Berlin"
        marker.map = map

    }

    //MARK: Get user location

    func getUserLocation(_ map: GMSMapView,_ locationManager: CLLocationManager) {

        var userLocation: String?

        locationManager.requestWhenInUseAuthorization()

        func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {

            if status == .authorizedWhenInUse {
                locationManager.startUpdatingLocation()

                map.isMyLocationEnabled = true
                map.settings.myLocationButton = true

            } else {
                setDefaultInitialLocation(map)
            }
        }

        func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {

            if let location = locations.first {

                map.camera = GMSCameraPosition(target: location.coordinate, zoom: 15, bearing: 0, viewingAngle: 0)

                locationManager.stopUpdatingLocation()

                //Store User Location
                userLocation = "\(location.coordinate.latitude), \(location.coordinate.longitude)"
                print("userLocation is: \((userLocation) ?? "No user Location")")

            }
        }
    }
}

This file has also this singelton:

// MARK: Shared Instance

    class func sharedInstance() -> GMSClient {
        struct Singleton {
            static var sharedInstance = GMSClient()
        }
        return Singleton.sharedInstance
    }

And then I call it in my view controller like this:

class MapViewController: UIViewController, CLLocationManagerDelegate {

    // MARK: Outlets

    @IBOutlet weak var mapView: GMSMapView!


    // MARK: Properties

    let locationManager = CLLocationManager()
    var userLocation: String?
    let locationManagerDelegate = GMSClient()


    // MARK: Life Cycle

    override func viewDidLoad() {

        super.viewDidLoad()

        self.locationManager.delegate = locationManagerDelegate

        GMSClient.sharedInstance().getUserLocation(mapView, locationManager)

    }

Anyone has an idea of what can be wrong?

Thanks!

Answer 1

Following what Paulw11 said, I found the faster solution using Notifications.

1. Send notification from the LocationManager delegate method inside the first view Controller:

   class MapViewController: CLLocationManagerDelegate {
   
       func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
   
                   if status == .authorizedWhenInUse {
                       locationManager.startUpdatingLocation()
   
                       mapView.isMyLocationEnabled = true
                       mapView.settings.myLocationButton = true
                   } else {
                       initialLocation()
                   }
               }
   
               func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
   
                   if let location = locations.first {
   
                       mapView.camera = GMSCameraPosition(target: location.coordinate, zoom: 15, bearing: 0, viewingAngle: 0)
   
                       locationManager.stopUpdatingLocation()
   
                       let userInfo : NSDictionary = ["location" : location]
   
                       NotificationCenter.default.post(name: NSNotification.Name("UserLocationNotification"), object: self, userInfo: userInfo as [NSObject : AnyObject])
   
                   }
               }
        }
   

2. Set the second view controller as observer. This way I can store the userLocation and use it later for the search request:

   class NeighbourhoodPickerViewController: UIViewController, UITextFieldDelegate {
   
   var userLocation: String?
   var currentLocation: CLLocation!
   
   override func viewDidLoad() {
       super.viewDidLoad()
   
       NotificationCenter.default.addObserver(self, selector: #selector(locationUpdateNotification), name: Notification.Name("UserLocationNotification"), object: nil)
   
   }
   
   func locationUpdateNotification(notification: NSNotification) {
       if let userInfo = notification.userInfo?["location"] as? CLLocation {
           self.currentLocation = userInfo
           self.userLocation = "\(userInfo.coordinate.latitude), \(userInfo.coordinate.longitude)"
       }
   }
   

Answer 2

I guess the problem is here,

self.locationManager.delegate = locationManagerDelegate

You have created a new instance of GMSClient, and saved it in the stored property and that instance is set as the delegate property of CLLocationManager.

You need to do this instead,

self.locationManager.delegate = GMSClient.sharedInstance()

You need to do this because you would want singleton instance of GMSClient to be the delegate for CLLocationManager and not a new instance. That way your singleton class would recieve the callbacks from CLLocationManager class.

To understand more about why your code was not working, I would suggest you read more about Objects, Instances, Instance variables, Singletons, Delegate design pattern.