title: Change images in UIImageView in sequence
body: <p>I want make something like animation.</p>
  
  <p>I have four UIImageView (names: IW1, IW2, IW3, IW4)
  I want change image in IW1 on image1 and next on image2, after that change image in IW2 on image1 and next on image2, after that change image in IW3 on image1 and next image2, after that change image in IW4 on image1 and next on image2.</p>
  
  <p>Unfortunately when I tried to do this, the only thing I could do is change the images in all UIImageViews at the same time, but I want to do it sequentially.</p>
  
  <p>Someone will help? </p>