Is it possible to use bind values using macruby?

I've been working through Hillegass' Cocoa Programming For Mac OS X, converting the exercises to MacRuby.

I've hit a big of a snag in the RaiseMan exercise though. It uses an NSArrayController as a binding for a table view. There is then a NSDocument called Person which is bound to provide the values for the table.

When I try to run this, I'm getting an error:

I've tried a number of different ways to make employees respond:

attr_accessor :employees

and also using a manual setter (in two different ways):

def employee=(val) end

def setEmployee(val) end

Neither seem to work.  Am I doing something wrong? Is this unimplemented?

I've looked at a RubyCocoa implementation of this exercise, and they just completely skip the NSArrayController and just set up a data source. 

Thanks for any help.

Brad