swift Avcapture session for barcode scanning is not working - swift

Question

I am trying to build a barcode scanner. I adapted some of this tutorial. The video capture session is working but it is not detecting any barcode. I have gone through the code multiple times and still could not find what the problem could be. Here is my code for detecting the barcode
class ScanController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {
var captureSession: AVCaptureSession?
var videoPreviewLayer: AVCaptureVideoPreviewLayer?
var qrCodeFrameView: UIView?
let supportedCodeTypes = [AVMetadataObject.ObjectType.upce,
AVMetadataObject.ObjectType.code39,
AVMetadataObject.ObjectType.qr]
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.default(for: AVMediaType.video)
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 = AVLayerVideoGravity.resizeAspectFill
videoPreviewLayer?.frame = view.layer.bounds
view.layer.addSublayer(videoPreviewLayer!)
// Start video capture.
captureSession?.startRunning()
// Add the message label
self.view.addSubview(messageLabel)
//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)
view.bringSubview(toFront: qrCodeFrameView)
}
} catch {
// If any error occurs, simply print it out and don't continue any more.
print("THERE IS A PROBLEM WITH THE CAPTURE SESSION *****************")
print(error)
return
}
}
}
what am I missing ?

Answer 1

maybe you missing the Delegate Methods? In the Tutorial is the delegate method :
optional func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection)
under the section Decoding the QR Code