import CoreLocation

class VCMain: ... , CLLocationManagerDelegate

lazy var locationManager: CLLocationManager = {
    let manager = CLLocationManager()
    manager.delegate = self
    manager.allowsBackgroundLocationUpdates = true
    return manager
}()
    
lazy var ibeaconRegion:CLBeaconRegion = {
    let proximityUUID = UUID(uuidString: beaconUuid)
    let region = CLBeaconRegion(proximityUUID: proximityUUID!, identifier: beaconRegionId)
    region.notifyEntryStateOnDisplay = true
    region.notifyOnEntry = true
    region.notifyOnExit = true
    return region
}()

func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
    switch status {
    case .restricted, .denied:
        // Disable your app's location features
        disableLocationServices()
        break

    case .authorizedAlways:
        // Enable any of your app's location services.
        self.enableLocationServices()
        break

    case .notDetermined, .authorizedWhenInUse:
        break
    }
}

func locationManager(_ manager: CLLocationManager, didStartMonitoringFor region: CLRegion) {
    manager.requestState(for: region)
}

func locationManager(_ manager: CLLocationManager, didDetermineState state: CLRegionState, for region: CLRegion) {
    if state == .inside {
        manager.startRangingBeacons(in: region as! CLBeaconRegion)
    } else {

    }
}

func locationManager(_ manager: CLLocationManager, didEnterRegion region: CLRegion) {
    if region is CLBeaconRegion {
        // Start ranging only if the feature is available.
        if CLLocationManager.isRangingAvailable() {
            manager.startRangingBeacons(in: region as! CLBeaconRegion)
        }
    }
}

func locationManager(_ manager: CLLocationManager, didExitRegion region: CLRegion) {
    // perform actions when exit region
}

func locationManager(_ manager: CLLocationManager, didRangeBeacons beacons: [CLBeacon], in region: CLBeaconRegion) {
        
    if self.ibeaconList.count > 0 && beacons.count <= 0 {
        manager.stopRangingBeacons(in: region)
        self.ibeaconList = []
        self.tableview.reloadData()
        return
    }

    if self.ibeaconList.count == 0 && beacons.count > 0 {
        self.performNotification(title: "Found new beacon devices", body: "Tap to view more details")
    }

    self.ibeaconList = []

    for aBeacon in beacons {
        let major = Int( CLBeaconMajorValue(truncating: aBeacon.major) )
        let minor = Int( CLBeaconMinorValue(truncating: aBeacon.minor) )

        var range = ""

        switch aBeacon.proximity {
        case .immediate:
            range = "Range : Immediate"
            break

        case .near:
            range = "Range : Near"
            break

        case .far:
            range = "Range : Far"
            break

        case .unknown:
            range = "Range : Unknown"
            break
        }

        self.ibeaconList.append(IBeaconItem(major: major, minor: minor, range: range))
    }

    self.tableview.reloadData()

}