RubyMotion OSX video recording sample

rubymotion_video_recording_sample.rb

class AppDelegate

  attr_accessor :captureMovieFileOutput

  def applicationDidFinishLaunching(notification)
    buildWindow
  end

  def buildWindow
    @av = AVScreenShackDocument.alloc.init
    @mainWindow = NSWindow.alloc.initWithContentRect([[240, 180], [800, 800]],
      styleMask: NSTitledWindowMask|NSClosableWindowMask|NSMiniaturizableWindowMask|NSResizableWindowMask,
      backing: NSBackingStoreBuffered,
      defer: false)
    @mainWindow.title = NSBundle.mainBundle.infoDictionary['CFBundleName']
    @mainWindow.orderFrontRegardless
    setupVideoBackground()
    add_buttons
    setup_recording
  end

  def add_buttons
    button = NSButton.alloc.initWithFrame([[0, 0], [100, 32]])
    button.title = "Record"
    button.action = "record:"
    button.target = self
    button.bezelStyle = NSRoundedBezelStyle
    button.autoresizingMask = NSViewMinXMargin|NSViewMinYMargin
    @mainWindow.contentView.addSubview(button)

    button = NSButton.alloc.initWithFrame([[200, 0], [100, 32]])
    button.title = "Stop"
    button.action = "stop:"
    button.target = self
    button.bezelStyle = NSRoundedBezelStyle
    button.autoresizingMask = NSViewMinXMargin|NSViewMinYMargin
    @mainWindow.contentView.addSubview(button)
  end

  def record(sender)
    puts "RECORDING"
    path = "video_record.mov"
    @captureMovieFileOutput.startRecordingToOutputFileURL(NSURL.fileURLWithPath(path), recordingDelegate:self) # <--- Problem
  end

  def stop(sender)
    puts "STOPPING"
    captureMovieFileOutput.stopRecording
  end

  def setupVideoBackground
    @vImagePreview = NSView.alloc.initWithFrame(CGRectMake(0,0,600,600))
    @vImagePreview.setWantsLayer(true)
    @mainWindow.contentView.addSubview(@vImagePreview)

    @session = AVCaptureSession.alloc.init
    @session.sessionPreset = AVCaptureSessionPresetHigh
   
    viewLayer = @vImagePreview.layer;
    captureVideoPreviewLayer = AVCaptureVideoPreviewLayer.alloc.initWithSession(@session)

    captureVideoPreviewLayer.frame = @vImagePreview.bounds
    @vImagePreview.layer.addSublayer(captureVideoPreviewLayer)
    display = CGMainDisplayID()
    device = AVCaptureScreenInput.alloc.initWithDisplayID(display)
    error_ptr = Pointer.new(:object)
    @session.addInput(device)
    @session.startRunning()

  end
  
  def setup_recording
    @captureMovieFileOutput = AVCaptureMovieFileOutput.alloc.init
    @captureMovieFileOutput.setDelegate(self)

    if @session.canAddOutput(@captureMovieFileOutput)
      @session.addOutput(@captureMovieFileOutput)
    end
  end

end