Rails - Aug 2006 - single-table inheritance and select

I''m getting some weirdness trying to use a select widget to choose  
the type from a collection of three objects sharing a database table  
via single-table inheritance (STI). I''d be grateful for any advice on  
whether it''s a bug or a feature, if a feature why and how I can more  
easily do what I''m trying to do.

So I have the usual STI setup, with a ''type'' field in the
table to
distinguish three objects, all subclasses of the same thing. It would  
seem logical to be able to create new objects by creating the  
superclass and setting the type along with all of the other fields --  
that way I can use one form to create all three. Unfortunately

<%= select ''<superclass>'', ''type'',
%w{a b c}  %> (where <superclass>
just stands for the name of my superclass)

blows up with an error: wrong argument type String (expected Module).

The obvious symbol-using variant does the same thing. So do the  
variants with ''class''. But

<%= text_field ''<superclass>'',
''type''  %> and
<%= select ''<superclass>'',
''<any_other_field_name>'', %w{a b c}  %>

both work fine.

Any clues as to what''s going on, why and how to fix / sidestep?
(I''ve
tried 1.1.6 as well as 1.1.4)

And, as we''re on the subject, should it be ''type'' or
''class''? Both
editions of the pragmatic book use ''type'' but there is the
occasional
message saying that this is deprecated. Or do we care?

thanks in advance


........................................................................ 
..........
John Browning