Polymorphic belongs to association - rafaellima/rails_admin GitHub Wiki

Synopsis:

class Comment < ActiveRecord::Base
  belongs_to :commentable, :polymorphic => true, :inverse_of => :comments
  attr_accessible :commentable_id, :commentable_type

  rails_admin do
    configure :commentable do
      # configuration here
    end
  end
end

# for info
class Team < ActiveRecord::Base
  has_many :comments, :as => :commentable, :inverse_of => :commentable
end

More here