title: Using an UIView as a Mask in another UIView on Swift
body: <p>I am developing an App on xCode with Swift. My screen has an Image of an animal (outlet "backImage"), over this image I have a view (outlet "coverView"), color black, which covers all the screen. So so far you can't see the animal image, because the "coverView" is in front of it. Then I have another view (outlet "maskView") which is smaller and it's over the big view "coverView". What I want is to use this "maskView" as mask and therefor see the "backImage" through it, like a window.</p>
  
  <p>Is there anyone out there able to figure this out?</p>
  
  <p>Here is my screen, I want to see the woman character behind the big gray view through the smaller white view:</p>
  
  <p><a href="https://i.stack.imgur.com/V6pYG.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/V6pYG.png" alt="enter image description here"></a></p>