title: are needsDisplayForKey/actionForKey overrides working correctly?
body: <p>I'm trying to convert some code that works in Objective-C to Swift.  The problem I'm running into is that needsDisplayForKey/actionForKey aren't getting called the same way. As far as I can tell, the custom key values aren't getting passed in correctly.   Here is what I get when I debug it:</p>
  
  <p>default value:</p>
  
  <pre><code>(String!) event = {
    core = {
      _baseAddress = Builtin.RawPointer = 0x00feee51 "onOrderIn"
      _countAndFlags = 1073741833
      _owner = Some {
        Some = (instance_type = Builtin.RawPointer = 0x01026348 @"onOrderIn")
      }
    }
  }
  </code></pre>
  
  <p>custom value (empty string passed in):</p>
  
  <pre><code>(String!) event = {
    core = {
      _baseAddress = Builtin.RawPointer = 0x0b418f79
      _countAndFlags = 1073741833
      _owner = Some {
        Some = (instance_type = Builtin.RawPointer = 0x0b418f70 -&gt; 0x006e38f0 (void *)0x006e38c8: __NSCFString)
      }
    }
  }
  </code></pre>
  
  <p>I'm not sure what the relevant code might be. I'll just ask - has anyone else was able to define a custom implicit animation in Swift? Is there anything I need to keep in mind when moving over from Objective C?</p>
  
  <pre><code>override class func needsDisplayForKey(key: String!) -&gt; Bool{
      if key == "angleFrom" || key == "angleTo" {
          return true;
      }
      return super.needsDisplayForKey(key)
  }
  
  override func actionForKey(event: String!) -&gt; CAAction!{
      if event == "angleFrom" || event == "angleTo" {
          return self.makeAnimationForKey(event)
      }
      return super.actionForKey(event)
  }
  </code></pre>