title: ios: add printing, but keep compatibility with ios 3
body: <p>i'm trying to add printing features to an ios app.
  while printing itself works fine, and the app works on ios > 4, i haven't figured out yet how to keep the ios 3.1 compatibility...</p>
  
  <p>i guess the issue is this: completionHandler:(UIPrintInteractionCompletionHandler)</p>
  
  <blockquote>
    <p>A block of type UIPrintInteractionCompletionHandler that you implement to handle the
    conclusion of the print job (for instance, to reset state) and to
    handle any errors encountered in printing.</p>
  </blockquote>
  
  <p>once i add the block:</p>
  
  <pre><code>void (^completionHandler)(UIPrintInteractionController *, BOOL, NSError *) =
  ^(UIPrintInteractionController *printController, BOOL completed, NSError *error) {
  };
  </code></pre>
  
  <p>the app won't even launch on iOS 3.1
  probably because blocks aren't available there.</p>
  
  <p>yes, i made sure that this code won't be run when launched on iOS 3.1...</p>
  
  <pre><code>if (([[[UIDevice currentDevice] systemVersion] floatValue] &gt;= 4.2) &amp;&amp; ([UIPrintInteractionController isPrintingAvailable]))
  </code></pre>
  
  <p>so i wonder if there's a way to have printing support for iOS >4.2, but keeping it to run on iOS 3.1?</p>
  
  <p>maybe there's a way to use a method instead of the "block"?
  or how would be the correct way to have printing available on supported iOS devices, and remain backwards compatible to iOS 3.1?</p>