tab/app/models/notification.rb

# == Schema Information
#
# Table name: notifications
#
#  id         :integer          not null, primary key
#  user_id    :integer          not null
#  message    :string
#  read       :boolean          default(FALSE)
#  created_at :datetime         not null
#  updated_at :datetime         not null
#

class Notification < ActiveRecord::Base
  belongs_to :user

  scope :unread, -> { where read: false }

  def read!
    update_attributes read: true
  end
end