Polymorphic has_many :through in Rails 2.3

gistfile1.rb

# A polymorphic has_many :through relationship in Rails 2.3
# based on Josh Susser's "The other side of polymorphic :through associations"
# http://blog.hasmanythrough.com/2006/4/3/polymorphic-through
class Authorship < ActiveRecord::Base
  belongs_to :author
  belongs_to :publication, :polymorphic => true
end

class Author < ActiveRecord::Base
  has_many :authorships
  with_options :through => :authorships, :source => :publication do |author|
    author.has_many :books,    :source_type => 'Book'
    author.has_many :articles, :source_type => 'Article'
  end

  def publications
    articles + books
  end
end

class Article < ActiveRecord::Base
  has_many :authorships, :as => :publication
  has_many :authors, :through => :authorships
end

class Book < ActiveRecord::Base
  has_many :authorships, :as => :publication
  has_many :authors, :through => :authorships
end