Why does locationManager popup immediately disappear when used in another class? - swift

Question

I am using the MapKit to use CLLocationManagerDelegate to get the user's location. If I were to request for the user's location in ViewController's viewDidLoad() function, then the popup appears, asking the user for the user's input. Note: the two properties required to ask for the location (Location When In Use, and Location Always And When In Use) is added to Info.plist
That is,
import UIKit
import MapKit
class ViewController: UIViewController, CLLocationManagerDelegate {
var locationManager: CLLocationManager?
override func viewDidLoad() {
super.viewDidLoad()
locationManager = CLLocationManager()
self.locationManager?.desiredAccuracy = kCLLocationAccuracyBest
self.locationManager?.requestWhenInUseAuthorization()
self.locationManager?.delegate = self
self.locationManager?.startUpdatingLocation()
}
}
The code above works fine; when the program begins, it show a popup asking the user for their location.
However, If I was to create a new class MapController and put the same code inside that class, and create a new instance of MapController inside viewDidLoad(), then the popup immediately disappears when the program is run.
That is,
import UIKit
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let mapController = MapController(viewController: self)
mapController.initialise()
}
}
import MapKit
class MapController: NSObject, CLLocationManagerDelegate {
private let viewController: UIViewController
private var locationManager: CLLocationManager
required init(viewController: UIViewController) {
self.viewController = viewController
locationManager = CLLocationManager()
}
func initialise() {
self.locationManager.desiredAccuracy = kCLLocationAccuracyBest
self.locationManager.requestWhenInUseAuthorization()
self.locationManager.delegate = self
self.locationManager.startUpdatingLocation()
}
}
When the code above is run, the popup asking for the user's location immediately disappears.
My question being: why does the popup stay when the locationManager code is in the viewDidLoad(), but when the code is separated into another class, and called into viewDidLoad(), it immediately disappears. Why does this happen?
How can I separate the locationManager code into another class without the popup immediately disappearing?

Answer 1

It's a memory management issue. In ViewController, you create a local variable named mapController in viewDidLoad. At the end of viewDidLoad, that MapController instance goes out of scope and gets deallocated.
Instead of using a local variable in viewDidLoad, create a property.
class ViewController: UIViewController {
var mapController: MapController!
override func viewDidLoad() {
super.viewDidLoad()
mapController = MapController(viewController: self)
mapController.initialise()
}
}
But this now creates a reference cycle since MapController is keeping a strong reference to the view controller.
So you also need to change the viewController property of MapController to be weak.