Unresolved Identifier "itemID" - ios

Question

How can I Globally define (barcode scanned) so that it can be accessible by all my functions. In order words how can I define “metadataObj” globally?
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()
}
}
I have one error when I tried to use ItemID within another function. I think this is because it is not globally defined, it is only defined within func captureOutput. Any ideas on how to globally define the barcode string values that I get from my barcode scanner?

Answer 1

You can move it beyond your class scopes, so it'll become global and visible through all your module

Answer 2

Declare it up here (where the comment is) to make it accessible.
class ScanController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var captureSession: AVCaptureSession?
var videoPreviewLayer: AVCaptureVideoPreviewLayer?
var qrCodeFrameView: UIView?
//DECLARE itemID here
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)

Answer 3

Just put "metadataObj" outside the class in the global scope (beginning of the file after the import section, I mean, outside the class declaration), so that it isn't a member of the class anymore (and initialize it with a value of your choice). If you declare it in a framework and want to use it in your app, then add the public access modifier, or you won't be able to access it.
If you want to put it in the scope of the class but accessible from everywhere in your code, add the static modifier (or static public if you declare it in a framework). Using static you'll create a single instance of the variable, not related to any particular instance of your class (one and only one instance of metadataObj shared among all instances of your class). Be careful if you access metadataObj from different threads... you could face very annoing faults, and difficult to fix. In this latter case consider thread synchronization (not exactly an easy subject to cope with)... I would discourage that if you haven't a very clear idea about what you need to do. If you, instead, need it only within the class scope (I mean, to be used by all the member functions... and only them), put it where Alec told you.