# File lib/active_record/attribute_methods/write.rb, line 25
      def write_attribute(attr_name, value)
        attr_name = attr_name.to_s
        attr_name = self.class.primary_key if attr_name == 'id' && self.class.primary_key
        @attributes_cache.delete(attr_name)
        column = column_for_attribute(attr_name)

        unless column || @attributes.has_key?(attr_name)
          ActiveSupport::Deprecation.warn(
            "You're trying to create an attribute `#{attr_name}'. Writing arbitrary " \
            "attributes on a model is deprecated. Please just use `attr_writer` etc."
          )
        end

        @attributes[attr_name] = type_cast_attribute_for_write(column, value)
      end