How do I serialize std::chrono::minutes

Question

How do I serialize std::chrono::minutes with cereal or in general?

I tried this

struct A {
    std::chrono::minutes m;

    template <class Archive>
    void serialize(Archive& ar) { 
        ar(m);
    }
};
int main()    
{
        A a;

        std::ostringstream os;
        cereal::JSONOutputArchive ar1(os);
        ar1(cereal::make_nvp("A", a));

        A result;
        std::istringstream is(os.str());
        cereal::JSONInputArchive ar2(is);
        ar2(cereal::make_nvp("A", result));

        if (a.m != result.m)
            std::cout << "error\n";
}

but get an error in Visual Studio 2015

1>   Types must either have a serialize function, load/save pair, or load_minimal/save_minimal pair (you may not mix these).
1>   Serialize functions generally have the following signature:
1>
1>   template<class Archive>
1>     void serialize(Archive & ar)
1>     {
1>       ar( member1, member2, member3 );
1>     }
1>
1>
1>  cereal.hpp(702): note: see reference to function template instantiation 'ArchiveType &cereal::InputArchive<ArchiveType,0>::processImpl<std::chrono::minutes,0>(const T &)' being compiled
1>          with
1>          [
1>              ArchiveType=cereal::JSONInputArchive,
1>              T=std::chrono::minutes
1>          ]

Ideally I wan to serialize and deserialize in a portable way.

I think I solved the problem by including cereal/types/chrono.hpp and changing to

#include <cereal/types/chrono.hpp>
class A {
    std::chrono::minutes m;

    friend class cereal::access;

    template <class Archive>
    void serialize(Archive& ar)
    { 
        ar(m);
    }
};

Answer 1

As you discovered, support for std::chrono::minute, which is really an std::chrono::duration, can be found by including cereal/types/chrono.hpp, which is included with cereal.