mostrar notificaciones a los usuarios cuando alguien comenta en su

debate o responde a su comentario

app/models/notification.rb

@@ -0,0 +1,12 @@
+class Notification < ActiveRecord::Base
+  belongs_to :user
+  belongs_to :activity
+
+  scope :unread, -> { where(read: false) }
+  scope :recent, -> { order(id: :desc) }
+  scope :for_render, -> { includes(activity: [:user, :trackable]) }
+
+  def timestamp
+    activity.trackable.created_at
+  end
+end