ios - 未解析的标识符 "itemID"

Question

我如何全局定义(条形码扫描)以便我的所有功能都可以访问它。换句话说，我如何全局定义“metadataObj”？

class ScanController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {

var captureSession: AVCaptureSession?
var videoPreviewLayer: AVCaptureVideoPreviewLayer?
var qrCodeFrameView: UIView?

override func viewDidLoad() {
super.viewDidLoad()

//Get an instance of the AVCaptureDevice class  a device object and provide the video as the media type parameter
let captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)

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

    // Initialize the captureSession object.
     captureSession = AVCaptureSession()

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

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

    // Start video capture.
    captureSession?.startRunning()

    //initialize QR Code Frame to highlight the QR Code

    qrCodeFrameView = UIView()
    if let qrCodeFrameView = qrCodeFrameView {
        qrCodeFrameView.layer.borderColor = UIColor.green.cgColor
        qrCodeFrameView.layer.borderWidth = 2
        view.addSubview(qrCodeFrameView)
    }
} catch {

    // If any error occurs, simply print it out and don't continue any more.
    print(error)
    return
}
}

 func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {

// Check if the metadataObjects array is not nil and it contains at least one object.
if metadataObjects == nil || metadataObjects.count == 0 {
    qrCodeFrameView?.frame = CGRect.zero
    messageLabel.text = "No QR/barcode is detected"
    return
}
//Get metadata object
let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject

if supportedCodeTypes.contains(metadataObj.type) {
    //if the found metadata is equal to the QR code metadata then update the status label's text and set the the bounds
    let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
    qrCodeFrameView?.frame = barCodeObject!.bounds

    if metadataObj.stringValue != nil {
        messageLabel.text = metadataObj.stringValue
        //Searches firebase for existing barcode
        }
        let itemToSearchFor = metadataObj.stringValue
        let itemID = metadataObj.stringValue
        guard let Description = productDescriptionTextField.text,
        let price = priceTextField.text,
        let location = productLocationTextField.text
        else{
            print("Fill basic product information")
            return
         }
        let ref = FIRDatabase.database().reference(fromURL: " /")
        // creating an  item child node
        let values = ["Item Description": Description, "Image": price, "Location": location, "Price": price ]

        let items = ref.child("Items").child(itemID!)
        items.updateChildValues(values, withCompletionBlock: { (err, ref) in
            if err != nil {
                print(err)
                return
            } })
         FIRDatabase.database().reference().child("Items").child(itemToSearchFor!).observeSingleEvent(of: .value, with:{(snap) in

                print(snap)

                    })

            self.setupNewProductEntry()
           self.setupenterNewProductButton()
}

            }

当我尝试在另一个函数中使用 ItemID 时出现一个错误。我认为这是因为它不是全局定义的，它只在 func captureOutput 内部定义。关于如何全局定义我从条码扫描仪获得的条码字符串值有什么想法吗？

Answer 1

你可以将它移到你的类范围之外，这样它就会变得全局并且在你的所有模块中可见