Swift 3如何限制用户只拍摄照片而不是视频- iOS，Xcode

   var captureSession: AVCaptureSession?

   var photoOutput: AVCapturePhotoOutput?

   var previewLayer: AVCaptureVideoPreviewLayer?

   override func viewDidLoad() {

       super.viewDidLoad()

       captureSession = AVCaptureSession()

       photoOutput = AVCapturePhotoOutput()

       guard let captureSession = captureSession, let photoOutput = photoOutput else {

           return

       }

       guard let backCamera = AVCaptureDevice.default(for: .video) else {

           return

       }

       do {

           let input = try AVCaptureDeviceInput(device: backCamera)

           if captureSession.canAddInput(input) && captureSession.canAddOutput(photoOutput) {

               captureSession.addInput(input)

               captureSession.addOutput(photoOutput)

           }

       } catch {

           print(error.localizedDescription)

       }

       previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)

       previewLayer?.videoGravity = .resizeAspectFill

       previewLayer?.frame = view.bounds

       view.layer.addSublayer(previewLayer!)

       captureSession.startRunning()

   }

   func capturePhoto() {

       guard let photoOutput = photoOutput else {

           return

       }

       let photoSettings = AVCapturePhotoSettings()

       photoSettings.flashMode = .auto

       photoOutput.capturePhoto(with: photoSettings, delegate: self)

   }

   func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {

       if let imageData = photo.fileDataRepresentation(), let image = UIImage(data: imageData) {

           // 处理拍摄到的照片

       }

   }

   @IBAction func takePhotoButtonTapped(_ sender: UIButton) {

       capturePhoto()

   }