更新由计时器驱动的函数中的变量

我有下面的功能,当一个按钮被切换到激活状态时,它可以正常工作。我想添加一个变量,它为每条消息提供从1开始的当前消息编号。我尝试过不同的设置/更新值的方法,但这些方法都没有帮助更新。

我对Swift/iOS开发非常陌生,所以我确信我遗漏了一些东西。我所知道的是,消息反复打印到控制台,直到按钮关闭,并且 Timer 使它能够连续运行。

@IBOutlet weak var stateLabel: UILabel!
//Starts / Stops recording of sensor data via a switch
@IBAction func stateChange(_ sender: UISwitch) {
    if sender.isOn == true {
        startSensorData()
        stateLabel.text = "Stop"
    } else {
        stopSensorData()
        stateLabel.text = "Start"
    }
}


func startSensorData() {
    print("Start Capturing Sensor Data")
    // Making sure sensors are available
    if self.motionManager.isAccelerometerAvailable, self.motionManager.isGyroAvailable {

        // Setting the frequency required for data session
        self.motionManager.accelerometerUpdateInterval = 1.0 / 3.0
        self.motionManager.gyroUpdateInterval = 1.0 / 3.0

        // Start sensor updates
        self.motionManager.startAccelerometerUpdates()
        self.motionManager.startGyroUpdates()

        // Configure a timer to fetch the data.
        self.motionUpdateTimer = Timer.scheduledTimer(withTimeInterval: 1.0/3.0, repeats: true, block: { (timer1) in
            // Get the motion data.
            var loggingSample = 1
            if let accelData = self.motionManager.accelerometerData, let gyroData = self.motionManager.gyroData {

                let accelX = accelData.acceleration.x
                let accelY = accelData.acceleration.y
                let accelZ = accelData.acceleration.z

                let gyroX = gyroData.rotationRate.x
                let gyroY = gyroData.rotationRate.y
                let gyroZ = gyroData.rotationRate.z

                let message = "\(Date().timeIntervalSince1970),\(self.device_id),\(loggingSample),\(accelX),\(accelY),\(accelZ),\(gyroX),\(gyroY),\(gyroZ),Processing"
                print(message)
                loggingSample += 1
            }
        }
    )}
}