When you monitor a region initialized with only UUID, didEnterRegion won't give you major and minor.

RangeWhileMonitorPart01.swift

import UIKit
import CoreLocation

class ViewController: UIViewController, CLLocationManagerDelegate {
    
    var manager = CLLocationManager()
    
    override func viewDidLoad() {
        super.viewDidLoad()

        manager.delegate = self
        manager.requestAlwaysAuthorization()
        
        if let uuid = NSUUID(UUIDString: "B9407F30-F5F8-466E-AFF9-25556B57FE6D") {
            let region = CLBeaconRegion(proximityUUID: uuid, identifier: uuid.UUIDString)
            manager.startMonitoringForRegion(region)
        }
    }
    
    // MARK: CLLocationManagerDelegate
    func locationManager(manager: CLLocationManager!, didEnterRegion region: CLRegion!) {
        if let region = region as? CLBeaconRegion {
            // region.major and region.minor will return nil
            println("Entered in region with UUID: \(region.proximityUUID) Major: \(region.major) Minor: \(region.minor)")
        }
    }
}