title: Invoke target action in Swift
body: <p>In Swift, how do I execute the Cocoa target-action pattern with a selector determined at runtime?</p>
  
  <p>The specifics at hand:
  My code receives a <code>UIBarButtonItem</code>, and it needs invoke the action that button represents.  In Objective-C, it's straightforward:</p>
  
  <pre><code>UIBarButtonItem* button = ...;
  [button.target performSelector: button.action withObject: self];
  </code></pre>
  
  <p>In Swift, <code>performSelector:</code> is not exposed for type/memory safety reasons.  I can't create a Swift closure since I don't know the button.action at compile time.  Any other technique for invoking the action?</p>