configure_dependency

# File activerecord/lib/active_record/associations/builder/belongs_to.rb, line 68
      def configure_dependency
        if options[:dependent]
          unless options[:dependent].in?([:destroy, :delete])
            raise ArgumentError, "The :dependent option expects either :destroy or :delete (#{options[:dependent].inspect})"
          end

          method_name = "belongs_to_dependent_#{options[:dependent]}_for_#{name}"
          model.send(:class_eval,             def #{method_name}              association = #{name}              association.#{options[:dependent]} if association            end, __FILE__, __LINE__ + 1)
          model.after_destroy method_name
        end
      end