title: How to clear the information from the Label.text?
body: <p>I am developing a QR code reader application. Hier is my code:</p>
  
  <pre><code>  var captureSession: AVCaptureSession?
    var videoPreviewLayer: AVCaptureVideoPreviewLayer?
    var qrCodeframeView: UIView?
  
  @IBOutlet weak var CancelButton: UIButton!
  @IBOutlet weak var Label: UILabel!
  override func viewDidLoad() {
  
  CancelButton.hidden = true
  Label.hidden = true
  
  
  super.viewDidLoad()
  // Do any additional setup after loading the view, typically from a nib.
   }
  
    override func didReceiveMemoryWarning() {
     super.didReceiveMemoryWarning()
  // Dispose of any resources that can be recreated.
   }
  
  
   @IBAction func ScanMe(sender: AnyObject) {
  
  CancelButton.hidden = false
  Label.hidden = false
  
  
  let captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
  
  var error: NSError?
  let input: AnyObject!
  
  do {
      input = try AVCaptureDeviceInput (device: captureDevice)
  } catch let error1 as NSError{
  
      error = error1
      input = nil
  
  }
  
  if (error != nil){
  print ("\(error?.localizedDescription)")
      return
  }
  captureSession = AVCaptureSession()
  
  captureSession?.addInput(input as! AVCaptureInput)
  
  let captureMetadatOutput = AVCaptureMetadataOutput()
  captureSession?.addOutput(captureMetadatOutput)
  
  captureMetadatOutput.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
  captureMetadatOutput.metadataObjectTypes = [AVMetadataObjectTypeQRCode]
  
  videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
  videoPreviewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
  videoPreviewLayer?.frame = view.layer.bounds
  view.layer.addSublayer(videoPreviewLayer!)
  
  captureSession?.startRunning()
  view.bringSubviewToFront(Label)
  view.bringSubviewToFront(CancelButton)
  
  qrCodeframeView = UIView()
  qrCodeframeView?.layer.borderColor = UIColor.greenColor().CGColor
  qrCodeframeView?.layer.borderWidth = 2
  view.addSubview(qrCodeframeView!)
  view.bringSubviewToFront(qrCodeframeView!)
  
  
  }
  
   func captureOutput(captureOutput: AVCaptureOutput!,    didOutputMetadataObjects metadataObjects: [AnyObject]!, fromConnection    connection: AVCaptureConnection!) {
  
  if metadataObjects == nil || metadataObjects.count == 0 {
  
      qrCodeframeView?.frame = CGRectZero
      Label.text = "No QR code detected"
      return
  }
  let metadateObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
  
  if metadateObj.type == AVMetadataObjectTypeQRCode {
  
      let BarcodeObject = videoPreviewLayer?.transformedMetadataObjectForMetadataObject(metadateObj as AVMetadataMachineReadableCodeObject) as! AVMetadataMachineReadableCodeObject
      qrCodeframeView?.frame = BarcodeObject.bounds
  
      if metadateObj.stringValue != nil {
  
          Label.text = metadateObj.stringValue
  
          captureSession?.stopRunning()
  
  
  
    }
     }
    }
  
  
     @IBAction func Cancel(sender: AnyObject) {
  CancelButton.hidden = true
  Label.hidden = true
  
  
  captureSession?.stopRunning()
  qrCodeframeView?.removeFromSuperview()
  videoPreviewLayer?.removeFromSuperlayer()
  
  
     }
  
     @IBAction func Open(sender: AnyObject) {
  
      }
      override func prepareForSegue(segue: UIStoryboardSegue, sender:   AnyObject?) {
      var PC : SecondSecondViewController = segue.destinationViewController as! SecondSecondViewController
     PC.label1 = Label.text!
     }
  
  
     }
  </code></pre>
  
  <p>The problem is when I click the cancel button and go back to the previous viewcontroller, when I reopen the qr code scanner I see the last scanned code, displayed in the Label.text. Would you please help me how to clear the label and do not display the old code, because these codes must be used only once and if the users see the codes they will be able to use them again.</p>