Extract nested parameter assignment to a separate method

activerecord/lib/active_record/attribute_assignment.rb

@@ -104,8 +104,7 @@ def assign_attributes(new_attributes, options = {})
         end
       end
 
-      # assign any deferred nested attributes after the base attributes have been set
-      nested_parameter_attributes.each { |k,v| _assign_attribute(k, v) }
+      assign_nested_parameter_attributes(nested_parameter_attributes) unless nested_parameter_attributes.empty?
       assign_multiparameter_attributes(multi_parameter_attributes) unless multi_parameter_attributes.empty?
     ensure
       @mass_assignment_options = previous_options
@@ -133,6 +132,11 @@ def _assign_attribute(k, v)
       end
     end
 
+    # Assign any deferred nested attributes after the base attributes have been set.
+    def assign_nested_parameter_attributes(pairs)
+      pairs.each { |k, v| _assign_attribute(k, v) }
+    end
+
     # Instantiates objects for all attribute classes that needs more than one constructor parameter. This is done
     # by calling new on the column type or aggregation type (through composed_of) object with these parameters.
     # So having the pairs written_on(1) = "2004", written_on(2) = "6", written_on(3) = "24", will instantiate
@@ -252,6 +256,5 @@ def type_cast_attribute_value(multiparameter_name, value)
     def find_parameter_position(multiparameter_name)
       multiparameter_name.scan(/\(([0-9]*).*\)/).first.first.to_i
     end
-
   end
 end