title: How to set corner radius of imageView?
body: <p>In Objective-C such line</p>
  
  <pre><code>self.mainImageView.layer.cornerRadius = CGRectGetWidth(self.mainImageView.frame)/4.0f;
  </code></pre>
  
  <p>does its job, I tried it in Swift using analogy</p>
  
  <pre><code>self.mainImageView.layer.cornerRadius = CGRectGetWidth(self.mainImageView.frame)/4.0
  </code></pre>
  
  <p>and it doesn't change anything, the corners are the same as before. Moreover, Xcode does not show any syntax errors. Does Swift support any other way to reach this goal? I checked some other threads here and usually it's getting done in Swift in the way showed above. </p>