1. Setup monitoring beacons

func initiateRegion(ref:BeaconHandler){
    let uuid: NSUUID = NSUUID(UUIDString: "<UUID>")
    let beacon = CLBeaconRegion(proximityUUID: uuid, identifier: "")
    locationManager?.requestAlwaysAuthorization()    //cllocation manager obj.
    beacon?.notifyOnEntry = true
    beacon?.notifyOnExit = true
    beacon?.notifyEntryStateOnDisplay = true
    locationManager?.startMonitoringForRegion(beacon!)
    locationManager?.delegate = self;
    // Check if beacon monitoring is available for this device
    if (!CLLocationManager.isMonitoringAvailableForClass(CLBeaconRegion)) {
        print("error")
    }
    locationManager!.startRangingBeaconsInRegion(self.beacon!)
}

2. Location manager enter and exit region

func locationManager(manager: CLLocationManager, didEnterRegion region: CLRegion) {
    if(region.isKindOfClass(CLBeaconRegion)) {
        locationManager!.startRangingBeaconsInRegion(self.beacon!)
    }
}
    
func locationManager(manager: CLLocationManager, didExitRegion region: CLRegion) {
    if(region.isKindOfClass(CLBeaconRegion)) {
        locationManager!.stopRangingBeaconsInRegion(self.beacon!)
    }
}

3. Location manager range beacon

func locationManager(manager: CLLocationManager, didRangeBeacons beacons: [CLBeacon], inRegion region: CLBeaconRegion) {
    print(beacons.first.major)
}

 beacon = CLBeaconRegion(proximityUUID: <#NSUUID#>, major: <#CLBeaconMajorValue#>, identifier: <#String#>) // listening to all beacons with given UUID and major value
 beacon =    CLBeaconRegion(proximityUUID: <##NSUUID#>, major: <##CLBeaconMajorValue#>, minor: <##CLBeaconMinorValue#>, identifier: <##String#>) // listening to all beacons with given UUID and major and minor value

First, you have to request authorization of location services

let locationManager = CLLocationManager()
locationManager.delegate = self
locationManager.requestWhenInUseAuthorization()
// OR locationManager.requestAlwaysAuthorization()

Then you can get all iBeacons' information inside didRangeBeacons

func locationManager(manager: CLLocationManager, didRangeBeacons beacons: [CLBeacon], inRegion region: CLBeaconRegion) {
    for beacon in beacons {
        print(beacon.major)
        print(beacon.minor)
    }
}