look in basic_archive.cpp Robert Ramey "Fred Lupien" wrote in message news:32e6d6bf0710241259r1eba133fofb924c86369498c4@mail.gmail.com... Yea I had thought about this but haven't tried it yet. I am working on this tonight. I have another question that could help me. Is their a documentation available on exactly what is serialized in the archive, the class format and related stuff seem to be serialized as a list of numbers (at least in text archive it appears so, forgive me if I am wrong). What is serialized exactly for each class (beside what the user specifies of course!)? If found that on a forum but I am not sure how relevant it is (from basic_archive.cpp) : ////////////////////////////////////////////////////////////////////// // // class_information is stored as // // class_id* // -1 for a null pointer // if a new class id // [ // exported key - class name* // tracking level - always/never // file version // ] // // if tracking // [ // object_id // ] // // [ // if a new object id // data... // ] // // * required only for pointers - optional for objects Thank you! On 10/19/07, Robert Ramey wrote: I've never thought about this, but my first attempt would be something like the following: template<class Archive> void load(Archiv &ar , C &c, const unsigned int version){ if(version < 4>) ar >> boost::serialization::base_object<A>(c); else ar >> boost::serialization::base_object<B>(c); } "Fred Lupien" wrote in message news:32e6d6bf0710190708x45191057ld2a23a92399f59e4@mail.gmail.com ... Hello, we are currently implementing serialization versioning using boost and I am curious to know if their is a way to support a changing class hierarchy. Let's say C derives from A for a while and then a change requires C to derive from B instead, which derives from A. Is it possible to support such a change provided we know what default values are needed for the new class? I tried and even if don't serialize anything in class C I get stream errors because I believe boost saves some base info for each class. When it tries to reload those value from a old stream, obviously it desynchronizes it because the values are not in the stream. So is their a way around this? Also is it possible to support the removal of a class. If, for exemple C derives from B which in turn derives from A and suddenly B is removed. Is their a way to deal with this without invalidating all previously saved data? *** I doubt it. If you want to load old archives, you have know how much to "skip" over. The only thing that MIGHT be possible is something like: template<class Archive> void load(Archiv &ar , C &c, const unsigned int version){ if(version < 4>){ class a; //no longer used ar >> a; // throw away old data on leaving scope } else ar >> boost::serialization::base_object<B>(c); } Thank you for your help! -- Frédérick Martel-Lupien Étudiant en Génie Informatique Université de Sherbrooke fred.lupien@gmail.com -------------------------------------------------------------------------- _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users -- Frédérick Martel-Lupien Étudiant en Génie Informatique Université de Sherbrooke fred.lupien@gmail.com ------------------------------------------------------------------------------ _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users