I've experimented with putting the category in a private, implementors-only header file and it seemed to work fine. But I'm not sure if that's canonical.

And thats all bad and why inheritance and encapsulation in obj C are kind of rough on you.

But on the other hand, it discourages something thats overused in other languages. Inheritance!

Obj-C would do well to find a better composition mechanism to make most of the inheritance issues a secondary concern.