Cocoa checks to see if the methods really are defined in the actualObjective C class. RubyCocoa doesn't actually define the methods - itrelies on forwardInvocation: (a bit like method_missing) to do itswork. Hence the problem you're seeing.
I wrote a helper method a while back called 'kvc_array_accessor',which you can see the source of in osx/oc_import.rb.
class Foo < OSX::NSObjectdef initialize@things = endkvc_array_accessor :thingsend
That should provide access to the ruby array @things. If you want toprovide access in a different way, just use the existingimplementations of 'countOfThings' etc that you have *after* callingkvc_array_accessor. That should overwrite the methods that are set upfor you in there.
I haven't tested this recently, and the above code hasn't been testedeither. Hopefully it'll give you enough to get going.