class DealsController
  private
  def collection
    @collection ||= Deal.order(order_attributes).page(params[:page])
  end

  def order_attributes
    DealOrderAttributes.build updated_at: :desc, params
  end
end

class DealOrderAttributes
  def initialize attributes, params
    @attributes = attributes

    @params = @params.fetch(:order, {})
  end

  def build
    @attributes.merge params
  end

  private
  def params
    #
    # build params
    #
  end
end