gistfile1.rb

        # Define an attribute reader method.  Cope with nil column.
        def define_read_method(symbol, attr_name, column)
          cast_code = column.type_cast_code('v') if column
          access_code = cast_code ? "(v=@attributes['#{attr_name}']) && #{cast_code}" : "@attributes['#{attr_name}']"

          unless attr_name.to_s == self.primary_key.to_s
            access_code = access_code.insert(0, "missing_attribute('#{attr_name}', caller) unless @attributes.has_key?('#{attr_name}'); ")
          end
          
          if cache_attribute?(attr_name)
            access_code = "@attributes_cache['#{attr_name}'] ||= (#{access_code})"
          end
          evaluate_attribute_method attr_name, "def #{symbol}; #{access_code}; end"
        end

        # Define read method for serialized attribute.
        def define_read_method_for_serialized_attribute(attr_name)
          evaluate_attribute_method attr_name, "def #{attr_name}; unserialize_attribute('#{attr_name}'); end"
        end
        
        # Defined for all +datetime+ and +timestamp+ attributes when +time_zone_aware_attributes+ are enabled.
        # This enhanced read method automatically converts the UTC time stored in the database to the time zone stored in Time.zone.
        def define_read_method_for_time_zone_conversion(attr_name)
          method_body = <<-EOV
            def #{attr_name}(reload = false)
              cached = @attributes_cache['#{attr_name}']
              return cached if cached && !reload
              time = read_attribute('#{attr_name}')
              @attributes_cache['#{attr_name}'] = time.acts_like?(:time) ? time.in_time_zone : time
            end
          EOV
          evaluate_attribute_method attr_name, method_body
        end