QR-сканер в XCode для обновления данных Firebase

Question

Я создал приложение для инвентаризации / управления оборудованием, которое включает в себя QR-сканер для проверки оборудования на входе / выходе. Это будет сканирование QR-кодов, которые содержат автоматически сгенерированные идентификаторы данных моего оборудования (например, -M89hHDwvkK27pO7Vc63), и я хотел бы выполнить код для обновления статуса и описания в моей базе данных Firebase.

В настоящий момент QR-сканер работает, и я могу распечатать идентификатор из QR-кода, и переход выполняется после сканера. Однако данные, похоже, не обновляются в Firebase.

Данные Firebase :

{
  "Equipment" : {
    "-M89hHDwvkK27pO7Vc63" : {
      "cat" : "cat1",
      "description" : "by A on 25/05/2020",
      "id" : "Item6",
      "status" : "in"
    },
    "-M89j3U504GYlJQyytlu" : {
      "cat" : "cat1",
      "description" : "by A on 25/05/2020",
      "id" : "item7",
      "status" : "in"
    },
    "-M9bIgc7GAj8kkdmYzzn" : {
      "cat" : "cat2",
      "description" : "by A on 12/06/2020",
      "id" : "item10",
      "status" : "in"
    },
    "-M9nvM1tMNNoU7_PoZNb" : {
      "cat" : "cat3",
      "description" : "by A on 15/06/2020",
      "id" : "item1",
      "status" : "in"
    },
    "-M9o5EGRLyEWrI9rPtU8" : {
      "cat" : "cat3",
      "description" : "by B on 15/06/2020",
      "id" : "item 2",
      "status" : "in"
    },

ViewController для QR-сканера:

class QRScannerViewController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {

    @IBOutlet weak var previewView: UIView!

    var imageOrientation: AVCaptureVideoOrientation?
    var captureSession: AVCaptureSession?
    var videoPreviewLayer: AVCaptureVideoPreviewLayer?
    var capturePhotoOutput: AVCapturePhotoOutput?

    var ref:DatabaseReference?
    var databaseHandler:DatabaseHandle?

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        // Get an instance of the AVCaptureDevice class to initialize a
        // device object and provide the video as the media type parameter
        guard let captureDevice = AVCaptureDevice.default(for: AVMediaType.video) else {
            fatalError("No video device found")
        }
        // handler chiamato quando viene cambiato orientamento
        self.imageOrientation = AVCaptureVideoOrientation.portrait

        do {
            // Get an instance of the AVCaptureDeviceInput class using the previous deivce object
            let input = try AVCaptureDeviceInput(device: captureDevice)

            // Initialize the captureSession object
            captureSession = AVCaptureSession()

            // Set the input device on the capture session
            captureSession?.addInput(input)

            // Get an instance of ACCapturePhotoOutput class
            capturePhotoOutput = AVCapturePhotoOutput()
            capturePhotoOutput?.isHighResolutionCaptureEnabled = true

            // Set the output on the capture session
            captureSession?.addOutput(capturePhotoOutput!)
            captureSession?.sessionPreset = .high

            // Initialize a AVCaptureMetadataOutput object and set it as the input device
            let captureMetadataOutput = AVCaptureMetadataOutput()
            captureSession?.addOutput(captureMetadataOutput)

            // Set delegate and use the default dispatch queue to execute the call back
            captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
            captureMetadataOutput.metadataObjectTypes = [AVMetadataObject.ObjectType.qr]

            //Initialise the video preview layer and add it as a sublayer to the viewPreview view's layer
            videoPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession!)
            videoPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
            videoPreviewLayer?.frame = view.layer.bounds
            previewView.layer.addSublayer(videoPreviewLayer!)

            //start video capture
            captureSession?.startRunning()

        } catch {
            //If any error occurs, simply print it out
            print(error)
            return
        }

    }

    override func viewWillAppear(_ animated: Bool) {
        navigationController?.setNavigationBarHidden(true, animated: false)
        self.captureSession?.startRunning()
    }

    // Find a camera with the specified AVCaptureDevicePosition, returning nil if one is not found
    func cameraWithPosition(position: AVCaptureDevice.Position) -> AVCaptureDevice? {
        let discoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .unspecified)
        for device in discoverySession.devices {
            if device.position == position {
                return device
            }
        }

        return nil
    }

    func metadataOutput(_ captureOutput: AVCaptureMetadataOutput,
                        didOutput metadataObjects: [AVMetadataObject],
                        from connection: AVCaptureConnection) {
        // Check if the metadataObjects array is contains at least one object.
        if metadataObjects.count == 0 {
            return
        }

        //self.captureSession?.stopRunning()

        // Get the metadata object.
        let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject

        if metadataObj.type == AVMetadataObject.ObjectType.qr {
            if let outputString = metadataObj.stringValue {
                DispatchQueue.main.async {
                    print(outputString)
//                    self.updatestatus(itemid: outputString)
                    let userEmail = Auth.auth().currentUser?.email
                    let userName = userEmail?.replacingOccurrences(of: "@email.com", with: "")
                    let date = Date()
                    let formatter = DateFormatter()
                    formatter.dateFormat = "dd/MM/yyyy"
                    let currentDate = formatter.string(from: date)
                    let description = "by " + userName! + " on " + currentDate
                    var statusdata = "-"
                    let ref = Database.database().reference().child("Equipment").child(outputString)
                    self.databaseHandler = ref.observe(.value, with: { (snapshot) in
                        let snapshotValue = snapshot.value as! [String:String]
                        print(snapshotValue["status"]!)
                        statusdata = snapshotValue["status"]! as String
                    })
                    if statusdata == "out" {
                        statusdata = "in"
                    } else {
                        statusdata = "out"
                    }
                    Database.database().reference().child("Equipment").child(outputString).updateChildValues(["status" : statusdata,"description":description])

                }
                    self.captureSession?.stopRunning()
                    self.performSegue(withIdentifier: "backtohome", sender: self)
            }
        }
    }
}

спасибо за вашу помощь в заранее!