Check Bluetooth status - Swift 4

Implement CBCentralManagerDelegate delegate for that.

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

Delegate method :

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    }}

you will need to use CBCentralManager and it provide delegate method "centralManagerDidUpdateState" https://developer.apple.com/documentation/corebluetooth/cbcentralmanager

func centralManagerDidUpdateState(_ central: CBCentralManager){    if central.state == .poweredOn    {        print("Searching for BLE Devices")        // Scan for peripherals if BLE is turned on    }    else    {        // Can have different conditions for all states if needed - print generic message for now, i.e. Bluetooth isn't On        print("Bluetooth switched off or not initialized")    }}