app/models/notification.rb
# == Schema Information
#
# Table name: notifications
#
# id :integer not null, primary key
# subject :string
# body :string
# short_message :string
# notification_source_id :integer
# notification_source_type :string
# created_at :datetime not null
# updated_at :datetime not null
#
class Notification < ActiveRecord::Base
belongs_to :notification_source, polymorphic: true
end