iOS-BlueCap-Example-04.swift

//we will next discover the "ec00" service in order be able to access its characteristics
let discoveryFuture = connectionFuture.flatMap { peripheral -> Future<Peripheral> in
    return peripheral.discoverServices([serviceUUID])
    }.flatMap { discoveredPeripheral -> Future<Service> in
        guard let service = discoveredPeripheral.service(serviceUUID) else {
            throw AppError.serviceNotFound
        }
        peripheral = discoveredPeripheral
        DispatchQueue.main.async {
            self.connectionStatusLabel.text = "Discovered service \(service.uuid.uuidString). Trying to discover characteristics"
            print(self.connectionStatusLabel.text!)
        }
        //we have discovered the service, the next step is to discover the "ec0e" characteristic
        return service.discoverCharacteristics([dateCharacteristicUUID])
}