MacRuby - ActiveRecord for storage?
Is it possible to use ActiveRecord for storage and query in a MacRuby Cocoa application?
If it is, are there any resources that shows how?
Are there any reason why ActiveRecord should not be used?
Yes, it is. It's a Ruby library, you can use it without any problem.
However, ActiveRecord is a quite huge library. You might not need all its features. If you simply need to connect to a database and perform operations, I strongly encourage you to give Sequel gem a try.