[Boost-users] Adding indexes + serialization for MultiIndex

Subject: [Boost-users] Adding indexes + serialization for MultiIndex
From: Sohail Somani (sohail_at_[hidden])
Date: 2013-02-27 12:52:49

I haven't actually happened upon this problem yet but I just want to 
know if I know how to deal with it for the future.

My question is: how does the serialization work (or not work) if we add 
or remove indexes from the type?

My suspicion is that one would have to do something like this:

// version 1:
BOOST_CLASS_VERSION(Thingy,1);

typedef multi_index_container<thing,indexes> myset1_t;

myset1_t m_MySet;

...
template<typename Ar>
void serialize(Ar & a, unsigned int)
{ ar & m_MySet; }

// version 2
BOOST_CLASS_VERSION(Thingy,2);

typedef multi_index_container<thing,indexes> myset1_t;
typedef multi_index_container<thing,indexes2> myset2_t;

myset2_t m_MySet; // using new version

...
template<typename Ar>
void serialize(Ar & a, unsigned int fv)
{
   if(Ar::is_loading && fv == 1)
   {
      myset1_t set;
      ar & set;
      m_MySet.clear();
      m_MySet.insert(m_MySet.begin(),set.begin(),set.end());
   }
   else
     ar & m_MySet;
}

Would this be OK, errors in syntax aside?

Thanks,

Sohail