configure_dependency_for_has_one

# File activerecord/lib/active_record/associations.rb, line 1019
        def configure_dependency_for_has_one(reflection)
          case reflection.options[:dependent]
            when :destroy, true
              module_eval "before_destroy '#{reflection.name}.destroy unless #{reflection.name}.nil?'"
            when :nullify
              module_eval "before_destroy '#{reflection.name}.update_attribute(\"#{reflection.primary_key_name}\", nil)'"
            when nil, false
              # pass
            else
              raise ArgumentError, "The :dependent option expects either :destroy or :nullify."
          end
        end