Something like Java annotations in Objective-C

I am looking for something like Java annotations (a way to mark a field or a method with metadata) in Objective c, but i can't find anything that is really a surrogate of this Java Feature. Is there a way to achieve the same result of a Java annotation in Objective-C ? Basically in the actual situation i'm trying to mark some fields in a class that i want to export with a serializer, i want to mark all fields in the class that have to be exported or serialized ... Is there some other way to mark those fields ?