Downcast from 'CLLocation?' to 'CLLocation' only unwraps optionals; did you mean to use '!'? - ios

Question

I'm trying to display the users current location on a map view but I'm getting an error on the first line of the location manager function
Here is my code
import UIKit
import MapKit
class FirstViewController: UIViewController, CLLocationManagerDelegate {
#IBOutlet weak var mapkitView: MKMapView!
var locationManager: CLLocationManager!
override func viewDidLoad()
{
super.viewDidLoad()
if (CLLocationManager.locationServicesEnabled())
{
locationManager = CLLocationManager()
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyBest
locationManager.requestAlwaysAuthorization()
locationManager.startUpdatingLocation()
}
}
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation])
{
let location = locations.last as! CLLocation
let center = CLLocationCoordinate2DMake(latitude: location.coordinate.latitude, longitude: location.coordinate.longitude)
let region = MKCoordinateRegion(center: center, span: MKCoordinateSpan(latitudeDelta: 0.01, longitudeDelta: 0.01))
self.mapkitView.setRegion(region, animated: true)
}
}
The error I'm getting is "Downcast from 'CLLocation?' to 'CLLocation' only unwraps optionals; did you mean to use '!'?
on line let location = locations.last as! CLLocation

Answer 1

You are force-casting an Optional CLLocationto CLLocation, that is why Swift suggests to simply force unwrap it:
let location = locations.last!
This version (and yours) will crash if locations is empty.
Thus I recommend to never force unwrap anything and use guardinstead:
guard let location = locations.last else {
return
}