displaypreview.swift

func displayPreview(on view: UIView) throws {
    guard let captureSession = self.captureSession, captureSession.isRunning else { throw CameraControllerError.captureSessionIsMissing }
        
    self.previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        self.previewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
    self.previewLayer?.connection?.videoOrientation = .portrait
    
    view.layer.insertSublayer(self.previewLayer!, at: 0)
    self.previewLayer?.frame = view.frame
}