Write methods against a collection of ActiveRecord objects

1_order_collection_extension.rb

module OrderCollectionExtension
  def revenue
    self.sum(:payment_total_in_cents)
  end
end

Order.non_zero_price.extend(OrderCollectionExtension).revenue

2_array_override.rb

# Probably going too far...

class Array # or would it be ActiveRelation?
  def initialize(*args)
    super
    begin
      extension_class = "#{first.class}CollectionExtension".constantize
      self.extend(extension_class)
    rescue NameError
    end
  end
end