I am trying to translate code that looks like this: static NSString *SKTWindowControllerCanvasSizeObservationContext = @"com.apple.SKTWindowController.canvasSize"; and later [[self document] addObserver:self forKeyPath:SKTDocumentCanvasSizeKey options:NSKeyValueObservingOptionNew context:SKTWindowControllerCanvasSizeObservationContext]; to Ruby: SKTWindowControllerCanvasSizeObservationContext = "com.apple.SKTWindowController.canvasSize" document.addObserver(self, forKeyPath: SKTDocumentCanvasSizeKey, options: NSKeyValueObservingOptionNew, context:SKTWindowControllerCanvasSizeObservationContext) but when it runs I get this error: expected instance of Pointer, got `"com.apple.SKTWindowController.canvasSize"' (String) (TypeError) How do I get the a pointer to the context string? All the examples I have found for the Pointer class seem to expect an objective C routing to fill it in. Thanks, Dave.