How to capture the URL used to launch an OS X application via URLScheme in Swift?

As far as I can tell from the documentation the classes takes the constant and converts it to the proper type:

func applicationWillFinishLaunching(aNotification: NSNotification?) {
    var appleEventManager:NSAppleEventManager = NSAppleEventManager.sharedAppleEventManager()
    appleEventManager.setEventHandler(self, andSelector: "handleGetURLEvent:withReplyEvent:", forEventClass: AEEventClass(kInternetEventClass), andEventID: AEEventID(kAEGetURL))
}