#include <fstream>
#include <iostream>
#include <vector>

#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/serialization/vector.hpp>
#include <boost/foreach.hpp>



class A {
public:
    A() : a(2) {}
    int a;
    template<class Archive> void serialize(Archive& ar, const unsigned int version)
    {
        ar & a;
    }
    
};


class B {
public:
    std::vector<A> v;
    template<class Archive> void serialize(Archive& ar, const unsigned int version)
    {
        ar & v;
    }
};



int main() {

    // Create a B that contains a vector of 3 A's.
    B b1;
    b1.v.resize(3);
    b1.v[0].a = 5;
    b1.v[1].a = 6;
    b1.v[2].a = 7;

    // Write it out.
    {
        std::ofstream ofs("data");
        boost::archive::text_oarchive oa(ofs);
        oa << b1;
    }

    // Load it back into a B that already contains 2 elements.
    B b2;
    b2.v.resize(2);
    b2.v[0].a = 20;
    b2.v[1].a = 21;
    {
        std::ifstream ifs("data");
        boost::archive::text_iarchive ia(ifs);
        ia >> b2;
    }
    BOOST_FOREACH(const A& a, b2.v) {
        std::cout << a.a << std::endl;
    }


}