Exemplo de código Swift

BluetoothWriter.swift

import Foundation
import CoreBluetooth

class BluetoothWriter : NSObject {
    
    private weak var peripheral: CBPeripheral!;
    private weak var characteristic:  CBCharacteristic!;
    
    init(peripheral : CBPeripheral, characteristic:CBCharacteristic) {
        self.peripheral = peripheral;
        self.characteristic = characteristic;
    }
    
    func writeData(value  :NSData){
        if (self.peripheral != nil && self.characteristic != nil) {
            self.peripheral.writeValue(value, forCharacteristic: self.characteristic, type: CBCharacteristicWriteType.WithoutResponse);
        }
    }
    
    func writeString(value : NSString){
        self.writeData(value.dataUsingEncoding(NSUTF8StringEncoding)!);
    }
    
    func writeColorWithRed(red : Int, green: Int, blue:Int){
        self.writeString(NSString(format:"c%d,%d,%d\n",red,green,blue));
    }
}