configure_dependency_for_has_one

# File activerecord/lib/active_record/associations.rb, line 1460
        def configure_dependency_for_has_one(reflection)
          if reflection.options.include?(:dependent)
            case reflection.options[:dependent]
              when :destroy
                method_name = "has_one_dependent_destroy_for_#{reflection.name}".to_sym
                define_method(method_name) do
                  association = send(reflection.name)
                  association.destroy unless association.nil?
                end
                before_destroy method_name
              when :delete
                method_name = "has_one_dependent_delete_for_#{reflection.name}".to_sym
                define_method(method_name) do
                  # Retrieve the associated object and delete it. The retrieval
                  # is necessary because there may be multiple associated objects
                  # with foreign keys pointing to this object, and we only want
                  # to delete the correct one, not all of them.
                  association = send(reflection.name)
                  association.delete unless association.nil?
                end
                before_destroy method_name
              when :nullify
                method_name = "has_one_dependent_nullify_for_#{reflection.name}".to_sym
                define_method(method_name) do
                  association = send(reflection.name)
                  association.update_attribute(reflection.primary_key_name, nil) unless association.nil?
                end
                before_destroy method_name
              else
                raise ArgumentError, "The :dependent option expects either :destroy, :delete or :nullify (#{reflection.options[:dependent].inspect})"
            end
          end
        end