Re: [Boost-users] [serialization] How to serialize an object usingareference to its base class ?

From: Robert Ramey (ramey_at_[hidden])
Date: 2006-09-28 09:12:45

Without seeing your program I couldn't suggest much.

Robert Ramey

"x y" <nosferatu_1_1_at_[hidden]> wrote in message 
news:20060928094242.89373.qmail_at_web31010.mail.mud.yahoo.com...
It works now, but only with XML archives. When I serialize into a binary 
archive I get a std::exception "bad alloc exception thrown".

I forgot to mention that I'm working with Borland C++ Builder 6, boost 
1_33_0

I also tried with gcc 3.2.3 on linux with boost 1_33_1 and it also works 
only with xml archives. With binary archive I get a "basic_string::resize" 
exception.

Robert Ramey <ramey_at_[hidden]> wrote:
This works for pointers - not references. - the following - along with 
compatible changes - should work.

Robert Ramey

void serialize(const base_class * src, std::ostream& dest) {
    boost::archive::binary_oarchive oa(dest);
    oa << BOOST_SERIALIZATION_NVP(src);
}

"x y" <nosferatu_1_1_at_[hidden]> wrote in message 
news:20060927081505.10666.qmail_at_web31012.mail.mud.yahoo.com...
Hi,

I'm new to boost and I'm having some trouble serializing an object using a 
reference to its base class.

Although there are a lot of messages related to this topic in the newsgroups 
and the doc, I did not find a workable answer to my proplem.

In the following code, the function serialize takes a reference to 
base_class as parameter. But the serialize method of derived_class is never 
called.

Did I miss something ?

Thanks for your help
Marc

#include <string>
#include <sstream>
#include <iostream>

#include <boost/archive/binary_oarchive.hpp>
#include <boost/archive/binary_iarchive.hpp>
#include <boost/serialization/string.hpp>
#include <boost/serialization/access.hpp>
#include <boost/serialization/is_abstract.hpp>
#include <boost/serialization/export.hpp>

using namespace std;

class base_class {
    friend class boost::serialization::access;

    public:
        base_class() : my_string("") { };
        base_class(string s) : my_string(s) { };
        virtual ~base_class() {};

        virtual void foo(void) = 0;

        template<class Archive>
        void serialize(Archive & ar, const unsigned int version)
        {
            ar & BOOST_SERIALIZATION_NVP(my_string);
        }

    public:
        string my_string;
};

BOOST_IS_ABSTRACT(base_class);
BOOST_CLASS_EXPORT(base_class);

class derived_class : public base_class {
    friend class boost::serialization::access;

    public:
        derived_class() : base_class(), my_int(0) {};
        derived_class(string s, int i) : base_class(s), my_int(i) {};
        virtual ~derived_class() {};

        void foo(void) {};

        template<class Archive>
        void serialize(Archive & ar, const unsigned int version)
        {
            ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(base_class)
               & BOOST_SERIALIZATION_NVP(my_int);
        }

        int my_int;
};

BOOST_CLASS_EXPORT(derived_class);

void serialize(const base_class& src, std::ostream& dest) {
    boost::archive::binary_oarchive oa(dest);
    oa << BOOST_SERIALIZATION_NVP(src);
}

int main(int argc, char** argv) {
    try {
        std::stringstream ss;

        derived_class d("aaa", 5);
        cout << "before: " << d.my_string << " " << d.my_int << endl;
        serialize(d, ss);

        // deserialize
        derived_class d2;
        boost::archive::binary_iarchive ia(ss);
        ia >> d2;
        cout << "after: " << d2.my_string << " " << d2.my_int << endl;
    }
    catch (const std::exception& ex) {
        cout << "std exception: " << ex.what() << endl;     }
    catch (...) {
        cout << "unknown exception" << endl;
    }
}

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