deserialization from an abstract base fails for bo

问题:

I'm able to serialize an object through an abstract base using boost::serialization. However, when I try to add deserialization, I get compile errors about the abstract base. Here's my serialization code that works:

/*
    g++ -Iinclude/ -Llib -lboost_serialization ~/Desktop/ser_ex.cpp -o stest
*/

#include <boost/serialization/serialization.hpp>
#include <boost/serialization/nvp.hpp>
#include <boost/archive/binary_oarchive.hpp>
#include <boost/serialization/vector.hpp>

#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <boost/serialization/export.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include <memory>

namespace bser = boost::serialization;
using namespace std;
namespace foo {
class AA
{
public:
    virtual void foo() = 0;
    virtual ~AA() {}
    std::string name;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar & name;
    }
};
BOOST_SERIALIZATION_ASSUME_ABSTRACT( AA );

class BB : public AA
{
public:
    virtual void foo() = 0;
    virtual void bar() = 0;
    virtual ~BB () {}
    int thing;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar.template register_type< AA >();
        ar & boost::serialization::base_object<AA>(*this);
        ar & thing;
    }
};
BOOST_SERIALIZATION_ASSUME_ABSTRACT( BB );

class CC : public BB
{
public:
    virtual void foo() {}
    virtual void bar() {}
    virtual ~CC() {}
    int otherThing;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar.template register_type< BB >();
        ar & boost::serialization::base_object<BB>(*this);
        ar & otherThing;
    }
};
}

BOOST_CLASS_EXPORT_KEY(foo::CC)
BOOST_CLASS_EXPORT_IMPLEMENT(foo::CC)


int main (int , char const **)
{
    std::vector< shared_ptr<foo::AA> > vv;
    vv.push_back( make_shared<foo::CC>() );

    std::ostringstream oss;
    boost::archive::binary_oarchive out_archive( oss );
    out_archive << vv;
    std::cout << oss.str() << std::endl;
}

Just add this line right below the include for binary_oarchive.hpp causes the code not to compile.

#include <boost/archive/binary_iarchive.hpp>

dawilcox-macOS:debug dawilcox$ make foo
dependencies: foo_main.o
building: foo_main.o
In file included from /Users/dawilcox/src/axle/foo_main.cpp:5:
In file included from /usr/local/include/boost/serialization/serialization.hpp:43:
/usr/local/include/boost/serialization/access.hpp:130:17: error: allocating an object of abstract class type 'foo::AA'
        ::new(t)T;

Boost is complaining that it can't instantiate my base type. That's kind of the point -- it's an abstract base type.

What's the proper way to deserialize an abstract base?

回答1:

Looks like the thing I have wrong is that I was registering against the base class in the deserialize function. So, I got rid of:

 ar.template register_type< AA >();

and changed

ar.template register_type< BB >();

to

ar.template register_type< CC >();

Here's my full code:

/*
    g++ -Iinclude/ -Llib -lboost_serialization ~/Desktop/ser_ex.cpp -o stest
*/

#include <boost/serialization/serialization.hpp>
#include <boost/serialization/nvp.hpp>
#include <boost/archive/binary_oarchive.hpp>
#include <boost/archive/binary_iarchive.hpp>
#include <boost/serialization/vector.hpp>
#include <OMNIMAKE/lib/boost_serialization>

#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <boost/serialization/export.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include <memory>

namespace bser = boost::serialization;
using namespace std;
namespace foo {
class AA
{
public:
    virtual void foo() = 0;
    virtual ~AA() {}
    std::string name;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar & name;
    }
};
BOOST_SERIALIZATION_ASSUME_ABSTRACT( AA );

class BB : public AA
{
public:
    virtual void foo() = 0;
    virtual void bar() = 0;
    virtual ~BB () {}
    int thing;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar & boost::serialization::base_object<AA>(*this);
        ar & thing;
    }
};
BOOST_SERIALIZATION_ASSUME_ABSTRACT( BB );

class CC : public BB
{
public:
    virtual void foo() {}
    virtual void bar() {}
    virtual ~CC() {}
    int otherThing;

    template<class Archive>
    void serialize(Archive & ar, unsigned int )
    {
        ar.template register_type< CC >();
        ar & boost::serialization::base_object<BB>(*this);
        ar & otherThing;
    }
};
}

BOOST_CLASS_EXPORT_KEY(foo::CC)
BOOST_CLASS_EXPORT_IMPLEMENT(foo::CC)


int main (int , char const **)
{
    std::vector< shared_ptr<foo::AA> > vv;
    vv.push_back( make_shared<foo::CC>() );

    std::ostringstream oss;
    boost::archive::binary_oarchive out_archive( oss );
    out_archive << vv;
    std::cout << oss.str() << std::endl;
}