title: Swift alternative to respondsToSelector:
body: <p>I was trying to implement swift's alternative to the <code>respondsToSelector:</code> syntax that was also shown in the keynote. </p>
  
  <p>I have the following: </p>
  
  <pre><code>protocol CustomItemTableViewCellDelegate {
      func changeCount(sender: UITableViewCell, change: Int)
  }
  </code></pre>
  
  <p>and then later in the code I call</p>
  
  <pre><code>class CustomItemTableViewCell: UITableViewCell {
  
     var delegate: CustomItemTableViewCellDelegate
     ...
     override func touchesEnded(touches: NSSet!, withEvent event: UIEvent!) {
        ...
        delegate?.changeCount?(self, change: -1)
     }
     ...
  }
  </code></pre>
  
  <p>I get the following errors</p>
  
  <ul>
  <li><code>Operand of postfix '?' should have optional type; type is
  '(UITableViewCell, change:Int) -&gt; ()'</code></li>
  <li><code>Operand of postfix '?' should
  have optional type; type is 'CustomItemTableViewCellDelegate'</code></li>
  <li><code>Partial application of protocol method is not allowed</code></li>
  </ul>
  
  <p>What I am doing wrong?</p>
  
  <p>Thanks</p>