Thanks Erel,
I had a feeling that would be the case, I did try writing a library to return an NSComparisonResult, but it wouldn't cast to an Object. Presumably because it's part of an Enum. You were correct when you said that Objective C is more complex than Java. I have an awful lot of learning to do.
Now you've implemented SortType in List, I'm sure I can achieve what I wanted using that. It was one of those, do it because you can experiments (or can't in this case). Experimenting is how I learn best.