c++ - Why make_nvp needs non-const reference? -


why non-const reference here?

template<class t> const nvp< t > make_nvp(const char * name, t & t);

the reason i'm asking have structure public fields , need make them private , use accessors instead. know if i'm allowed use temporary variable , pass them make_nvp or need befriend serializer data structure.

// option 1 auto = data.geta(); ar & make_nvp("a", a);  // option 2 ar & make_nvp("a", data._a); // _a private, serializer friend

i don't know ar because it's templated parameter, in cases make use of non-constness , save later use , option 1 problematic.

in boost archive, can use single function both serialization , deserialization. achieved using archive template argument - can output archive serializes structure or input archive loads struct file. deserialization function needs non-const reference store deserialized value , that's why make_nvp needs non-const reference.

coming question: option 2 makes more sense, because option 1 breaks deserialization.


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