polymorphic for banister

gistfile1.txt

user = User.create!
announcement = Announcement.create!

user.user_news << UserNews.create! subject: announcement

site_announcement.rb

class SiteAnnouncement < ActiveRecord::Base
  has_many :user_news, :as => :subject
end

user.rb

class User < ActiveRecord::Base
  has_many :user_news
end

user_comment.rb

class FriendRequest < ActiveRecord::Base
  has_many :user_news, :as => :subject

  belongs_to :user
  belongs_to :target_user, class_name: 'User', foreign_key: :target_user_id
end

user_news.rb

class UserNews < ActiveRecord::Base
  belongs_to :subject, polymorphic: true
  belongs_to :user
end