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!

You have nested your delegate functions inside your `getUserLocation` function. This won't work. Move them out. — Paulw11, Jul 08 '17 at 10:04
I tried that before and did it worked, the thing is I would like to create later a completion handler in order to get the user location for a google map web search request. Something like... `func getUserLocation(_ map: GMSMapView,_ locationManager: CLLocationManager, completionHandlerForUserLocation: @escaping (_ userLocation: String?, _ error: NSError?) -> Void)) {` so I didn't know how to do it using the delegate methods... — celiux, Jul 08 '17 at 10:15
To be honest a completion handler probably isn't the right pattern here. You could use NSNotification or you could set a delegate or store a closure in a property. I would probably use an NSNotification since that allows you to easily notify multiple observers — Paulw11, Jul 08 '17 at 10:18
Oh I see, I never used NSNotifications. I will check! Thanks to your answer I found this [thread](https://stackoverflow.com/questions/11513259/ios-cllocationmanager-in-a-separate-class), it's quite old but I think it can solve my problem. I'll give updates later! — celiux, Jul 08 '17 at 10:37

celiux · Accepted Answer · 2017-07-08T15:22:37.087

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

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])

                }
            }
     }

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)"
    }
}

Puneet Sharma · Answer 2 · 2017-07-08T09:42:24.937

1

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.

edited Jul 08 '17 at 09:42

answered Jul 08 '17 at 09:37

Puneet Sharma

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Thanks for your reply. Do you mean to better do this? locationManager.delegate = self. But it doesn't work neither. I also tryied to delete it and still the same... – celiux Jul 08 '17 at 09:41
Set the singleton instance as delegate as I mentioned in the answer. – Puneet Sharma Jul 08 '17 at 09:50
1

I made what you said but still the same. Maybe is not a problem of the delegation? Yep, I know... I spend hours reading about that programming foundations but still very difficult to aprehend, I guess it will come with time once I start doing real stuff. But I will research today more specially about that singelton/shared instances and delegates. – celiux Jul 08 '17 at 10:06

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

2 Answers2