controllers/polymorphic_resource/base.rb

#
# Indexes, creates and deletes entries of a collection
# To be subclassed
#
class PolymorphicResource::Base < InheritedResources::Base

  actions :index, :create
  respond_to :json, :xml

  def create
    authorize! :create, build_resource
    resource.user = current_user

    super do |format|
      format.html do
        if resource.errors.empty?
          render :partial => resource
        else
          render :partial => 'form', :status => :unprocessable_entity
        end
      end
    end
  end

  def destroy
    authorize! :destroy, resource
    resource.destroy
    head :ok
  end
end