Construct object from boost serialization archive

Question

Is it possible to construct objects from directly from the archive?

Something like this...

// Non-working pseudo code
struct Foo {
    BOOST_SERIALIZATION_SPLIT_MEMBER();
    std::vector<int> data;

    Foo() {
        // populate "data" by doing calculation
        data.push_back(1); data.push_back(2);
    }

    template<class Archive>
    Foo( Archive & ar ) {
        // populate "data" by rading the archive
    }

    template<class Archive>
    void save(Archive & ar, const unsigned int version) const {
        // Normal serialization of data
        ar << data;
    }
};

int main(int argc, const char *argv[])
{
    // deserialize
    boost::archive::text_iarchive oar(std::cin);
    Foo foo(oar);

    return 0;
}

Answer 1

You can use a deserializing constructor:

#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>

#include <fstream>

class Point
{
public:
    Point() = default;
    Point(boost::archive::text_iarchive& archive)
    {
        archive >> *this;
    }

    float x = 1.;
    float y = 2.;

private:
    friend class boost::serialization::access;

    template<class TArchive>
    void serialize(TArchive & archive, const unsigned int version)
    {
        archive & x;
        archive & y;
    }
};


int main()
{
    Point p;
    p.x = 5;
    p.y = 6;

    std::ofstream outputStream("test.archive");
    boost::archive::text_oarchive outputArchive(outputStream);
    outputArchive << p;
    outputStream.close();

    std::ifstream inputStream("test.archive");
    boost::archive::text_iarchive inputArchive(inputStream);

    Point pointRead(inputArchive);

    std::cout << pointRead.x << " " << pointRead.y << std::endl;

    return 0;
}