var manager:CBCentralManager!

 viewDidLoad() {      // Or init()
     manager          = CBCentralManager()
     manager.delegate = self
 }

func centralManagerDidUpdateState(_ central: CBCentralManager) {
    switch central.state {
    case .poweredOn:
        break
    case .poweredOff:
        print("Bluetooth is Off.")
        break
    case .resetting:
        break
    case .unauthorized:
        break
    case .unsupported:
        break
    case .unknown:
        break
    default:
        break
    }
}