title: Animating UIButton images
body: <p>I'd like to give a UIButton in my app a continuous "pulsing" effect where it animates through a series of images and then reverses back through these same images. I've found examples of UIImageViews using their animationImages property, but all I've found for UIButtons is animating changing their alpha. </p>
  
  <p>The UIView method setAnimationRepeatAutoreverses is what I want for the looping, but I don't understand how to use an array of images within an animation block for a UIButton. Is this possible or is a NSTimer/setImage approach recommended? Any examples are much appreciated.</p>