My question is essentially the same as this one: http://stackoverflow.com/questions/1168047/polymorphic-association-with-multiple-associations-on-the-same-model

However, the proposed/accepted solution does not work, as illustrated by a commenter later.

I have a Photo class that is used all over my app. A post can have a single photo. However, I want to re-use the polymorphic relationship to add a secondary photo.

Before:

class Photo 
   belongs_to :attachable, :polymorphic => true
end

class Post
   has_one :photo, :as => :attachable, :dependent => :destroy
end

Desired:

class Photo 
   belongs_to :attachable, :polymorphic => true
end

class Post
   has_one :photo,           :as => :attachable, :dependent => :destroy
   has_one :secondary_photo, :as => :attachable, :dependent => :destroy
end

However, this fails as it cannot find the class "SecondaryPhoto". Based on what I could tell from that other thread, I'd want to do:

   has_one :secondary_photo, :as => :attachable, :class_name => "Photo", :dependent => :destroy

Except calling Post#secondary_photo simply returns the same photo that is attached via the Photo association, e.g. Post#photo === Post#secondary_photo. Looking at the SQL, it does WHERE type = "Photo" instead of, say, "SecondaryPhoto" as I'd like...

Thoughts? Thanks!