How do I override the mouseDragged() function for NSButton on MacOS?

Question

I have a MacOS app which uses NSButton objects. The button is set to style "Push" and type "Push On Off".

I have created a class called DraggableButton which attempts to override the function:

override func mouseDragged(event: NSEvent){
     print("Mouse dragged!")
}

However it only overrides it if I also override this function AND refrain from calling super:

mouseDown(event: NSEvent){
     //Do Nothing. Everything works
}

If mouseDown is empty, then mouseDragged gets called. If however mouseDown calls super.mouseDown(event), or if I do not override mouseDown at all, then mouseDragged does not get called. Unfortunately, these actions disable the normal mouseDown functions.

mouseDown(event: NSEvent){
     super.mouseDown(event: event) //Now mouseDragged stops working
}

In short, how to I override mouseDragged without breaking the mouseDown function?