Swift Beacon doesn't work now using Swift 3.0 - swift

Question

I have been following a guide to using Swift to create a Beacon proximity app, but since updating Xcode and updating the code to Swift 3.0 I am getting a fatal error.
Going through the functions I think there is an issue with the startScanning function, when it fires I get fatal error message.
Any hints at to what could help would be greatly appreciated:
import UIKit
import CoreLocation
class ViewController: UIViewController, CLLocationManagerDelegate {
#IBOutlet weak var distanceLabel: UILabel!
var locationManager: CLLocationManager!
override func viewDidLoad() {
super.viewDidLoad()
locationManager = CLLocationManager()
locationManager.delegate = self
locationManager.requestAlwaysAuthorization()
view.backgroundColor = UIColor.gray
print("did load")
}
func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
if status == CLAuthorizationStatus.authorizedAlways{
print("status authorized")
if CLLocationManager.isMonitoringAvailable(for: CLBeaconRegion.self){
print("is monitoring")
if CLLocationManager.isRangingAvailable() {
print("scanning")
startScanning()
}
}
}
}
func startScanning() {
print("start Scanning")
let uuid = NSUUID(uuidString: "695e5f08824c785cadc72e1dde23be04")
let beaconRegion = CLBeaconRegion(proximityUUID: uuid as! UUID, identifier: "MyBeacon")
locationManager.startMonitoring(for: beaconRegion)
locationManager.startRangingBeacons(in: beaconRegion)
}
func updateDistance(distance: CLProximity){
UIView.animate(withDuration: 1) { [unowned self] in
switch distance {
case .unknown:
self.view.backgroundColor = UIColor.gray
self.distanceLabel.text = "UNKNOWN"
print("distance Unknown")
case .far:
self.view.backgroundColor = UIColor.blue
self.distanceLabel.text = "FAR"
print("distance Far")
case .near:
self.view.backgroundColor = UIColor.orange
self.distanceLabel.text = "NEAR"
print("distance Near")
case .immediate:
self.view.backgroundColor = UIColor.red
self.distanceLabel.text = "BOOM!"
print("distance Immediate")
}
}
}
func locationManager(_ manager: CLLocationManager, didRangeBeacons beacons: [CLBeacon], in region: CLBeaconRegion) {
if beacons.count > 0 {
let beacon = beacons.first! as CLBeacon
updateDistance(distance: beacon.proximity)
print("found more than one beacon")
} else {
updateDistance(distance: .unknown)
print("found only one beacon")
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}

Answer 1

The problem is that your UUID is in the wrong format, so this line fails to parse it, assigning nil to the variable uuid:
let uuid = NSUUID(uuidString: "695e5f08824c785cadc72e1dde23be04")
The program will then crash using the uuid as! UUID operation because ! will crash if there is a nil value.
To fix this, you need to add dashes at the appropriate places in the UUID string. You should also avoid using the ! operator to force unwrap optional variables in Swift, as it can cause crashes like this. Try this:
if let uuid = NSUUID(uuidString: "695e5f08-824c-785c-adc7-2e1dde23be04") {
let beaconRegion = CLBeaconRegion(proximityUUID: uuid, identifier: "MyBeacon")
locationManager.startMonitoring(for: beaconRegion)
locationManager.startRangingBeacons(in: beaconRegion)
}
else {
NSLog("Invalid UUID format")
}
When running check that the code does not go down the "Invalid UUID format" path.