Rails - Oct 2009 - Single Table Inheritance (STI) Broken: NameError

Some how I''m getting NameError: uninitialized constant when accessing a
child models that inherits form the parent model.  However, if I access
the parent model first, then the child model is resolved.

What am I doing wrong?  My steps are below...

Thanks,
Francis.
> ./script/generate model Blah type:string
class CreateBlahs < ActiveRecord::Migration
  def self.up
    create_table :blahs do |t|
      t.string :type

      t.timestamps
    end
  end

  def self.down
    drop_table :blahs
  end
end

> rake db:migrate
==  CreateBlahs: migrating
===================================================-- create_table(:blahs)
   -> 0.0989s
==  CreateBlahs: migrated (0.0991s)
==========================================
blah.rb:
class Blah < ActiveRecord::Base
end

class Whale < Blah
end

class Dolphin < Blah
end

> ./script/console 
>> Dolphin.new
NameError: uninitialized constant Dolphin
  from
/Library/Ruby/Gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:443:in
`load_missing_constant''
  from
/Library/Ruby/Gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:80:in
`const_missing''
  from
/Library/Ruby/Gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependencies.rb:92:in
`const_missing''
  from (irb):1
>> Blah.new
=> #<Blah id: nil, type: nil, created_at: nil, updated_at:
nil>
>> Dolphin.new
=> #<Dolphin id: nil, type: "Dolphin", created_at: nil,
updated_at: nil>
-- 
Posted via http://www.ruby-forum.com/.

On Oct 13, 9:21 am, Albert Wong
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> Some how I''m getting NameError: uninitialized constant when
accessing a
> child models that inherits form the parent model.  However, if I access
> the parent model first, then the child model is resolved.
>
> What am I doing wrong?  My steps are below...
>
When the constant Dolphin is hit for the first time and is not already
loaded, rails expects to find it in dolphin.rb, which doesn''t exist
(and at this point rails can''t know that Dolphin and Blah are
related). If you touch Blah then blah.rb is loaded which will also
cause Dolphin to be loaded. Either stick to the file naming
conventions that allow rails to guess where to load classes from or
don''t rely on it working.

Fred
> Thanks,
> Francis.
>
> > ./script/generate model Blah type:string
>
> class CreateBlahs < ActiveRecord::Migration
>   def self.up
>     create_table :blahs do |t|
>       t.string :type
>
>       t.timestamps
>     end
>   end
>
>   def self.down
>     drop_table :blahs
>   end
> end
>
> > rake db:migrate
>
> ==  CreateBlahs: migrating
> ===================================================> --
create_table(:blahs)
>    -> 0.0989s
> ==  CreateBlahs: migrated (0.0991s)
> ==========================================>
> blah.rb:
> class Blah < ActiveRecord::Base
> end
>
> class Whale < Blah
> end
>
> class Dolphin < Blah
> end
>
> > ./script/console
> >> Dolphin.new
>
> NameError: uninitialized constant Dolphin
>   from
> /Library/Ruby/Gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependen
cies.rb:443:in
> `load_missing_constant''
>   from
> /Library/Ruby/Gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependen
cies.rb:80:in
> `const_missing''
>   from
> /Library/Ruby/Gems/1.8/gems/activesupport-2.3.2/lib/active_support/dependen
cies.rb:92:in
> `const_missing''
>   from (irb):1>> Blah.new
>
> => #<Blah id: nil, type: nil, created_at: nil, updated_at:
nil>>> Dolphin.new
>
> => #<Dolphin id: nil, type: "Dolphin", created_at: nil,
updated_at: nil>
> --
> Posted viahttp://www.ruby-forum.com/.

Fred you are the man!  That was exactly the problem... Thanks for all 
the help!...

Frederick Cheung wrote:
> When the constant Dolphin is hit for the first time and is not already
> loaded, rails expects to find it in dolphin.rb, which doesn''t
exist
> (and at this point rails can''t know that Dolphin and Blah are
> related). If you touch Blah then blah.rb is loaded which will also
> cause Dolphin to be loaded. Either stick to the file naming
> conventions that allow rails to guess where to load classes from or
> don''t rely on it working.
> 
> Fred
-- 
Posted via http://www.ruby-forum.com/.