[boost] question about flyweight

3 Feb 2008

      I've spent a tiny amount of time looking over the flyweight documentation 
and some code and I have a couple minor observations along with a really 
dumb question.

a) when I see boost::flyweight::flyweights it confuses me.  I suppose its no 
big deal.

b) I'm curious about the serialization implementation.  Why didn't you 
choose just to serialize the factory?  This seems to me the most obvious 
implementation and I wonder why you didn't feel it was a good choice.

template<
class Archive,
typename T,typename Arg1,typename Arg2,typename Arg3
...
void serialize(
Archive& ar,const ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3>& f,
const unsigned int version)
{
    typedef ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3> flyweight;
    ar & flyweight::factory(); // serialization tracking guarentees only one 
copy
    ar & f.h;                         // serialization tracking optimizes 
down to an integer object id
}

This might not be a good idea if flyweight reference count isn't used.  So 
another idea might be:

template<
class Archive,
typename T,typename Arg1,typename Arg2,typename Arg3
...
void save(
Archive& ar,const ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3>& f,
const unsigned int version)
{
    typedef ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3> flyweight;
    ar << f.h;                         // serialization tracking optimizes 
down to an integer object id
}

template<
class Archive,
typename T,typename Arg1,typename Arg2,typename Arg3
...
void load(
Archive& ar,const ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3>& f,
const unsigned int version)
{
    typedef ::boost::flyweights::flyweight<T,Arg1,Arg2,Arg3> flyweight;
    T t;
    ar >> t;                         // serialization tracking optimizes 
down to an integer object id
    f.factory.insert(t);          // or something along those lines
    //fix up object address of t - off hand I don't remember the syntax
}

In short, I don't see why a "helper" is required.

Robert Ramey