From: Mauricio Fernandez <mfp@...>
Date: 2006-08-07T18:21:36+09:00
Subject: Re: Superclass mismatches

On Mon, Aug 07, 2006 at 05:10:11PM +0900, listrecv@gmail.com wrote:
> irb(main):015:0> ResellerCategory
> => Taxonomy::ResellerCategory
> irb(main):016:0> ResellerCategory.superclass
> => Taxonomy::Category
> irb(main):017:0> ResellerCategory.superclass == Taxonomy::Category
> => false
[...] 
> irb(main):018:0> ResellerCategory.superclass.object_id
> => 46413760
> irb(main):019:0> Taxonomy::Category.object_id
> => 47673490
[...]
> irb(main):020:0> module Taxonomy; class ResellerCategory < Category;
> end ; end
> TypeError: superclass mismatch for class ResellerCategory
> irb(main):023:0> module Taxonomy; class ResellerCategory <
> ResellerCategory.superclass; end ; end
> => nil
> 
> My questions are:
> 1) How did that happen?  It seems like 1 != 1

Taxonomy::Category has been redefined, as if you were doing
  module Taxonomy; Category = Class.new { ... } end 
or maybe
  module Taxonomy; remove_const :Category; class Category; ... end end
and that were being evaluated more than once.
Can you show the code?

> 2) More importantly, how can I stop this error from happening?  (It's
> caused when the file defining ResellerCategory is loaded a second time)

You have to make sure that Taxonomy::Category references the same class all
the time. If you can't find why it's changing, you can get by with
    module Taxonomy; class ResellerCategory < Category; end end 
which must be eval()ed only once, and then replacing in the file to be loaded
repeatedly
  class ResellerCategory < Category
with
  class ResellerCategory

HTH
-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby