title: Swift equivalent for @protocol(DelegateType)
body: <p>I'm working with ReactiveCocoa in Swift. I need to use the following method:</p>
  <p><code>rac_signalForSelector(selector: Selector, fromProtocol: Protocol?)</code></p>
  <p>Passing the selector works fine with <code>Selector(&quot;method:&quot;)</code>, but I cannot find how to pass the delegate protocol to the <code>fromProtocol</code> parameter.</p>
  <p>What is the proper way to pass the Protocol type from a delegate to a method signature like this?</p>
  <p><strong>EDIT: Adding method documentation and best attempt</strong></p>
  <p>The documentation for this method is as follows:</p>
  <blockquote>
  <p><strong>selector</strong> - The selector for whose invocations are to be observed. If it doesn’t exist, it will be implemented using information from protocol, and may accept non-object arguments and return a value. This cannot have C arrays or unions as arguments or return type.</p>
  <p><strong>protocol</strong> - The protocol in which selector is declared. This will be used for type information if the selector is not already implemented on the receiver. This must not be NULL, and selector must exist in this protocol.</p>
  </blockquote>
  <p><del>I have tried sending in <code>DelegateType.self</code>, and I end up receiving this error:</p>
  <blockquote>
  <p>Could not find an overload for <code>rac_signalForSelector</code> that accepts the supplied arguments</del></p>
  </blockquote>