如何干燥named_scope扩展名

  named_scope :by_order, :order => \'priority ASC\' do
    def total_points
      self.sum(\'point_value\')
    end
  end

  named_scope :required, :conditions => [\'bonus = ?\', false] do
    def total_points
      self.sum(\'point_value\')
    end
  end

  named_scope :bonus, :conditions => [\'bonus = ?\', true] do
    def total_points
      self.sum(\'point_value\')
    end
  end

class Thing << ActiveRecord::Base

   scope :in_priority_order, order(\"priority\")
   scope :no_bonus, where(:bonus => false)
   scope :with_bonus, where(:bonus => true)
   scope :total_points, sum(:point_value)

   def self.total_bonus_points
      with_bonus.total_points
   end

   def self.total_no_bonus_points
      no_bonus.total_points
   end
end