QR code is not working - Delegate method is not getting called

Question

I have seen many threads and tutorials regarding this but nothing solved my problem. I have followed this tutorial for implementing simple QR code application but code is not getting detected.In most of QR related question the issue was related to delegate methods old name. I have verified it that i am using updated delegate method but still its not working.

This is my code. Any one can please highlight which silly mistake i am doing.

import UIKit 
import AVFoundation

class QRScannerController: UIViewController, AVCaptureMetadataOutputObjectsDelegate {

    @IBOutlet var messageLabel:UILabel!
    @IBOutlet var topbar: UIView!

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

    let supportedCodeTypes = [AVMetadataObjectTypeQRCode,
                              AVMetadataObjectTypeCode39Code,
                              AVMetadataObjectTypeUPCECode,
                              AVMetadataObjectTypeCode39Mod43Code,
                              AVMetadataObjectTypeEAN13Code,
                              AVMetadataObjectTypeEAN8Code,
                              AVMetadataObjectTypeCode93Code,
                              AVMetadataObjectTypeCode128Code,
                              AVMetadataObjectTypePDF417Code,
                              AVMetadataObjectTypeAztecCode,
                              AVMetadataObjectTypeInterleaved2of5Code,
                              AVMetadataObjectTypeITF14Code,
                              AVMetadataObjectTypeDataMatrixCode] as [String]

    override func viewDidLoad() {
        super.viewDidLoad()

        // Get an instance of the AVCaptureDevice class to initialize 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)

            // Initialize a AVCaptureMetadataOutput object and set it as the output device to the capture session.
            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()

            // Move the message label and top bar to the front
            view.bringSubview(toFront: messageLabel)
            view.bringSubview(toFront: topbar)

            // 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(error)
            return
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    // MARK: - AVCaptureMetadataOutputObjectsDelegate Methods

    func metadataOutput(_ output: AVCaptureMetadataOutput, didOutput metadataObjects: [AVMetadataObject], from connection: AVCaptureConnection) {

        // Check if the metadataObjects array is not nil and it contains at least one object.
        if metadataObjects.count == 0 {
            qrCodeFrameView?.frame = CGRect.zero
            messageLabel.text = "No QR/barcode is detected"
            return
        }

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

        if supportedCodeTypes.contains(where: { $0 == metadataObj.type }) {
            // If the found metadata is equal to the QR code metadata then update the status label's text and set the bounds
            let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
            qrCodeFrameView?.frame = barCodeObject!.bounds

            if metadataObj.stringValue != nil {
                messageLabel.text = metadataObj.stringValue
            }
        }
    }
     }

I am testing it on iPod with iOS version 9.3.5 and the code is in swift 3 with xcode 8.3.2.

Answer 1

on iOS 10.x metadataOutput is called captureOutput. Change the name and the signature and it should work flawlessly:

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