Boost MPL to generate code for object serialization?

Question

I want to generate serialization/deserialization code for

class Object
{
    string a;
    int b;
    long c;
    char d;
};

by looking at a mpl sequence, but I need to be able to identify object and retrieve it back as well, I can't figure out how would I get the names of it members, do I have to know it?

code should look like

void SerializeObject(ostream os)
{
   serialize(object.a, os);
   serialize(object.b, os);

   //serialize(object.member, os);
}

I want to generate above code by user only defining a mpl sequence corresponding the object layout, is it doable, can you give me some hints?

my aim is:

User defines mpl::vector<String, int, long, char> for above object and my metaprogram can generate the coded needed.

Answer 1

Consider a boost::fusion, and use the macro BOOST_FUSION_ADAPT_STRUCT() to promote your structure to a fusion sequence (random access), e.g. once you've defined the above structure, you can do something like

BOOST_FUSION_ADAPT_STRUCT(
    Object,
    (std::string, a)
    (int, b)
    (long, c)
    (char, d)
)

Now that it's been promoted, you can simply use a for_each to iterate over the members, something like:

template<typename archive>
struct serializer {
   serializer(archive& ar):ar(ar) {}

   template<typename T>
   void operator()(const T& o) const {
      ar & o;  // assuming binary for example...
   }
   archive& ar;
};

template<typename archive, typename sequence>
void serialize(archive& ar, sequence const& v) {
   boost::fusion::for_each(v, serializer<archive>(ar));
}

To use, it should be as simple as:

Object foo; // instance to serialize
serialize(<archive>, foo);