Improve attribute value computation.

lib/active_model/serializer/attributes.rb

@@ -5,8 +5,8 @@ module Attributes
 
       included do
         with_options instance_writer: false, instance_reader: false do |serializer|
-          serializer.class_attribute :_attribute_mappings # @api private : maps attribute key names to names to names of implementing methods, @see #attribute
-          self._attribute_mappings ||= {}
+          serializer.class_attribute :_attribute_procs # @api private : maps attribute key names to names to names of implementing methods, @see #attribute
+          self._attribute_procs ||= {}
           serializer.class_attribute :_attribute_keys # @api private : maps attribute names to keys, @see #attribute
           self._attribute_keys ||= {}
         end
@@ -17,15 +17,24 @@ def attributes(requested_attrs = nil, reload = false)
           @attributes = nil if reload
           @attributes ||= self.class._attribute_keys.each_with_object({}) do |(name, key), hash|
             next unless requested_attrs.nil? || requested_attrs.include?(key)
-            hash[key] = self.class._attribute_mappings[name].call(self)
+            hash[key] = _attribute_value(name)
+          end
+        end
+
+        # @api private
+        def _attribute_value(name)
+          if self.class._attribute_procs[name]
+            instance_eval(&self.class._attribute_procs[name])
+          else
+            read_attribute_for_serialization(name)
           end
         end
       end
 
       module ClassMethods
         def inherited(base)
           super
-          base._attribute_mappings = _attribute_mappings.dup
+          base._attribute_procs = _attribute_procs.dup
           base._attribute_keys = _attribute_keys.dup
         end
 
@@ -54,16 +63,7 @@ def attributes(*attrs)
         #     end
         def attribute(attr, options = {}, &block)
           _attribute_keys[attr] = options.fetch(:key, attr)
-          _attribute_mappings[attr] = _attribute_mapping(attr, block)
-        end
-
-        # @api private
-        def _attribute_mapping(name, block)
-          if block
-            ->(instance) { instance.instance_eval(&block) }
-          else
-            ->(instance) { instance.read_attribute_for_serialization(name) }
-          end
+          _attribute_procs[attr] = block
         end
 
         # @api private