instance method association_constructor_method

# File activerecord/lib/active_record/associations.rb, line 1528
        def association_constructor_method(constructor, reflection, association_proxy_class)
          redefine_method("#{constructor}_#{reflection.name}") do |*params|
            attributees      = params.first unless params.empty?
            replace_existing = params[1].nil? ? true : params[1]
            association      = association_instance_get(reflection.name)

            unless association
              association = association_proxy_class.new(self, reflection)
              association_instance_set(reflection.name, association)
            end

            if association_proxy_class == HasOneAssociation
              association.send(constructor, attributees, replace_existing)
            else
              association.send(constructor, attributees)
            end
          end
        end