title: UIImageView and multi-threading
body: <p>In <a href="http://developer.apple.com/library/ios/#releasenotes/General/WhatsNewIniOS/Articles/iPhoneOS4.html" rel="nofollow">What's New in iOS 4</a>, it is mentioned that <code>UIImage</code> drawing is now safe if done in a background thread.  However, when working with <code>UIImageView</code>, in most cases simple assignment to the image property:</p>
  
  <pre><code>imageView.image = [UIImage imageNamed:@"..."]
  </code></pre>
  
  <p>is preferred over drawing for performance reasons (because <code>UIImageView</code> can make better use of GPU this way).</p>
  
  <p>My question is: is assigning to <code>imageView.image</code> safe if done in a background thread?  In general UIKit requires work to be done in the main thread, so I am hesitant.</p>
  
  <p>If it's not safe, what is the best way to make use of the fact that <code>UIImage</code> drawing is safe in non-UI thread when working with <code>UIImageView</code>?</p>