Write Ruby extension in Objective-C

I just recently started developing Ruby scripts, and may I say it’s
interesting that I can build a nice application with comparatively few
lines of code.

I would like to write an extension for Ruby that works on Mac OS X.
However, I’m used to developing iOS apps using Objective-C and Cocoa
Touch’s Foundation framework, and I would rather develop a library in a
similar fashion and use that library in a Ruby extension. I am aware
that Objective-C is a subset of C, but I would rather not use C.