How to make UISlider's “track” invisible?

Question

I\'m trying to emulate Apple\'s \"Slide to Unlock\" feature in my application. I get to this point (image below), but as you can see the UISlider\'s \"track\" is visible and is

Answer 1

In Swift:

slider.setMinimumTrackImage(UIImage(), forState: .Normal)
slider.setMaximumTrackImage(UIImage(), forState: .Normal)