If an object is serialized (saved) from a pointer, the loading part automatically
creates (instantiates) a new object. However, there are situations when
the object is already created and all we need is to restore its state.
The following code demonstrates one possible - although not elegant - solution using a temporary object:#include <fstream>
#include <iostream>
#include
#include
#include
#include
class A
{
public:
A()
: m_val(100)
{
}
int m_val;
private:
friend class boost::serialization::access;
template <typename Archive>
void serialize(Archive &ar, const unsigned int version)
{
ar & BOOST_SERIALIZATION_NVP(m_val);
}
};
int main(int argc, char* argv[])
{
A *a = new A();
// Save the object
{
std::ofstream os("d:/test.xml");
boost::archive::xml_oarchive oa(os);
// Save from pointer
oa & BOOST_SERIALIZATION_NVP(a);
}
// Change the object state
a->m_val = 200;
// Restore the state
{
std::ifstream is("d:/test.xml");
boost::archive::xml_iarchive ia(is);
A* aTemp;
ia & BOOST_SERIALIZATION_NVP(aTemp);
a->m_val = aTemp->m_val; // Copy object state
assert(a->m_val == 100);
delete aTemp;
}
}
Here is my question: Is there some more convenient way to restore the object state? In other words, is it possible to prevent creation of a new object and just 'populate' an existing object?
