swift - 将 Int 转换为 NSData

Question

大家好，我需要将我的 iPhone 中的值写入 BLE 外围设备。

发现了服务和特征，并且连接也在那里。

问题：我需要将值 2 写入特征。为此我打电话

peripheral.writeValue(data, forCharacteristic: characteristic, 
type: CBCharacteristicWriteType.WithResponse)

数据应该是 2 但它应该来自 NSData 类型。我从 int 到 NSData 的转换的结果是02000000而不是2，特征需要 2。

这种转换有什么问题？如何获得值为2的 NSData

    var ring = 2

    //Convert 2 to NSData -> for peripheral.writeValue()
    let data = NSData(bytes: &ring, length: sizeof(NSInteger))

    //---> let data is <02000000> should be <2>
    print(data)

以下代码是我需要 NSData 中的值 2 的上下文

func peripheral(peripheral: CBPeripheral, didUpdateValueForCharacteristic characteristic: CBCharacteristic, error: NSError?) {

    var data1 = characteristic.descriptors

    //print("\(data1.dynamicType)")
    //print(data1)
    var ring = 2

    //Convert 2 to NSData -> for peripheral.writeValue()
    let data = NSData(bytes: &ring, length: sizeof(NSInteger))//sizeof(NSInteger))

    //---> let data is <02000000> should be <2>
    print(data)


    //Write Datat to peripheral ( characteristic )
    peripheral.writeValue(data, forCharacteristic: characteristic, type: CBCharacteristicWriteType.WithResponse)

}

func peripheral(peripheral: CBPeripheral, didWriteValueForCharacteristic characteristic: CBCharacteristic, error: NSError?) {
    print("Value is Written")

}

十分感谢。