<ivo.t@moss-soft.de> wrote in message news:ECB13B9D09204914A385D25B334DF831@Ivo2...

Hi to everybody,

I'm new to the list, work for some time with Boost and C++ and have a

fair knowledge but am not an expert yet. I try to serialize a map whose type

This is really a question for the boost users group, but...

ist not default-constructible, and I'm seriously stuck there. I thought the load_construct_data and save_construct_data overrides would help me there, but that seems not to be the case. I tried to create a private default constructor hoping that the map (respectively pair) constructor could access

This is because boost::serialization does not put any special handling in for std::pair when serialized via std::map. It is the default construction of the pair that trips you up.

it, due to the boost::serialization::access friend declaration, but that didn't work as well. I really do _not_ want to make a public default constructor. What could I do as a workaround??

You could specialize the construct_data functions for the pair (i.e. the map's value_type), e.g.: //////// // Example, non-default constructable class class X { public: X(int i) : i_(i) {} private: int i_; friend class boost::serialization::access; template <typename A> void serialize(A &ar, const unsigned) { ar & i_; } }; template <typename A> inline void load_construct_data(A &ar, X * x, const unsigned) { ::new(x)X(1); // e.g. } //////// typedef std::map<int, X> Map; typedef Map::value_type PairType; template <typename A> inline void serialize(A &ar, PairType &p, const unsigned) { // Do nothing, handled by xxxx_construct_data } template <typename A> inline void save_construct_data(A &ar, const PairType *p, const unsigned v) { using namespace boost::serialization; ar << make_nvp("first", p->first); save_construct_data(ar, &p->first, v); ar << make_nvp("second", p->second); save_construct_data(ar, &p->second, v); } template <typename A> inline void load_construct_data(A &ar, PairType *p, const unsigned v) { using namespace boost::serialization; typedef BOOST_DEDUCED_TYPENAME boost::remove_const<PairType::first_type>::type typef; load_construct_data(ar, &const_cast<typef &>(p->first), v); ar >> make_nvp("first", const_cast<typef &>(p->first)); load_construct_data(ar, &p->second, v); ar >> make_nvp("second", p->second); }