WKNavigationDelegate only works if set to self

I am writing a Swift Hybrid application and I need to be able to know when my WKWebView has finished loading a request. I am attempting to use WKNavigationDelegate to achieve this. However, the only way I can get the events to fire is if I set it this way: ``` webView.navigationDelegate = self ``` The problem is I have some data that I want associated with my request, so I created a custom class that implements WKNavigationDelegate that looks like this: ``` class MyNavigationDelegate : NSObject, WKNavigationDelegate { init(...) { //set local variables with passed args } func webView(webView: WKWebView, didFinishNavigation navigation: WKNavigation!) { println("finished loading") } } ``` then I assign it like this: ``` webView.navigationDelegate = MyNavigationDelegate(my, arguments, here) webView.loadRequest(...) ``` The page is loading so there is no problem with how I'm loading it. What am I missing?