[Boost-users] [serialization] serialize type-erasure

Subject: [Boost-users] [serialization] serialize type-erasure
From: oswin krause (oswin.krause_at_[hidden])
Date: 2014-09-30 05:55:22

Hi list,

i am currently trying to serialize a type-erasure, but i am not sure how 
this should be done exactly. Before boost 1.56 we used the polymorphic 
archives and a base class to implement serialization, but since they are 
broken in 1.56 and a few users are nagging me (plus i can't compile the 
library myself any more after a mandatory upgrade...), i have to get it 
right.

my setup looks like this

class ErasureBase{
     ....
};

template<class T>
class Erasure{
public:
     Erasure (T& foo):m_foo(foo){}
     template<class Archive>
     void serialize(Archive & ar, const unsigned int){
         ar & m_foo;
     }
private:
     T& m_foo;
};

class MyClass{
public:
     template<class T>
     MyClass(T& foo):m_wrapper(new Erasure<T>(foo)){}
     template<class Archive>
     void serialize(Archive & ar, const unsigned int){
         ar & *m_wrapper;
     }
private:
     boost::scoped_ptr<ErasureBase> m_wrapper;

};

in the usage of MyClass i assume that serialisation/deserialisation is 
only to be called on constructed objects of type MyClass, therefore i do 
not need capabilities to deserialize from pointers. The question is: how 
do I tell the archive which Erasure<T> exist? The solutions in the 
tutorial pages only look at the cases where Erasure<T> is serialized 
directly or where it is known which classes are to be serialized (and i 
don't assume my users to know which Erasure<T> are instantiated...).

If there exists a solution for this: is the solution also stable wrt the 
order of registration of classes?

Best,
Oswin

The ques