How to do a sliding transition in RubyMotion?

sliding_transition.rb

def viewDidLoad
  view.image = UIImage.imageNamed('welcome.png')

  view.userInteractionEnabled = true
  recognizer = UITapGestureRecognizer.alloc.initWithTarget(self, action:'nextScreen')
  view.addGestureRecognizer(recognizer)
end

def nextScreen
  animation = CATransition.animation
  animation.duration = 0.5
  animation.type = KCATransitionMoveIn
  animation.subtype = KCATransitionFromRight
  view.layer.addAnimation(animation, forKey:'imageTransition')
  view.image = UIImage.imageNamed('pic2.png')
end

Source: http://stackoverflow.com/a/5057691/424300