define_attribute_method

# File activemodel/lib/active_model/attribute_methods.rb, line 259
      def define_attribute_method(attr_name)
        attribute_method_matchers.each do |matcher|
          method_name = matcher.method_name(attr_name)

          unless instance_method_already_implemented?(method_name)
            generate_method = "define_method_#{matcher.method_missing_target}"

            if respond_to?(generate_method, true)
              send(generate_method, attr_name)
            else
              define_optimized_call generated_attribute_methods, method_name, matcher.method_missing_target, attr_name.to_s
            end
          end
        end
        attribute_method_matchers_cache.clear
      end