AVCodeReader-init.swift

override init() {
  super.init()

  //Make sure the device can handle video
  guard let videoDevice = AVCaptureDevice.default(for: .video),
        let deviceInput = try? AVCaptureDeviceInput(device: videoDevice) else {
      return
  }
  
  //session
  captureSession = AVCaptureSession()

  //input
  captureSession?.addInput(deviceInput)

  //output
  let captureMetadataOutput = AVCaptureMetadataOutput()
  captureSession?.addOutput(captureMetadataOutput)
  captureMetadataOutput.setMetadataObjectsDelegate(self, queue: DispatchQueue.main)
  //interprets qr codes only
  captureMetadataOutput.metadataObjectTypes = [.qr]

  //preview
  guard let captureSession = captureSession else { return }
  let captureVideoPreview = AVCaptureVideoPreviewLayer(session: captureSession)
  captureVideoPreview.videoGravity = .resizeAspectFill
  self.videoPreview = captureVideoPreview
}