How to serialize a boost::uuid with cereal - c++

Question

Trying to serialize this simple class:
class Data
{
public:
Data();
Data(boost::uuids::uuid id);
Data(const Data&) = delete;
Data& operator=(const Data&) = delete;
inline boost::uuids::uuid getGuid() { return guid; }
template <class Archive>
void serialize(Archive & ar)
{
ar(guid);
}
private:
boost::uuids::uuid guid;
};
But I get this error message
error C2338: Trying to serialize an unserializable type with an output archive.
Poiting to the uuid. The boost serialization way to enable this would be to add
#include <boost/uuid/uuid_serialize.hpp>
but this doesn't work for cereal out of the box. Cereal documentation says
cereal archives operate on either an std::ostream or std::istream object.
so I tried adding the header where there are defined but no luck
#include <boost/uuid/uuid_io.hpp>

Answer 1

This worked with cereal JSON archives. I also included in comment a way to do it for a binary archive.
#ifndef CEREAL_TYPES_BOOST_UUID_
#define CEREAL_TYPES_BOOST_UUID_
#include <boost/uuid/uuid.hpp>
#include <boost/uuid/uuid_io.hpp>
#include <boost/lexical_cast.hpp>
namespace cereal
{
template <class Archive> inline
void save(Archive& ar, boost::uuids::uuid const& uuid)
{
std::string val = boost::lexical_cast<std::string>(uuid);
ar(val);
// Other approach, probably better for binary
//ar(make_size_tag(static_cast<size_type>(uuid.size())));
//for (auto it = uuid.begin(), end = uuid.end(); it != end; ++it)
// ar(*it);
}
template <class Archive> inline
void load(Archive& ar, boost::uuids::uuid& uuid)
{
std::string val;
ar(val);
uuid = boost::lexical_cast<boost::uuids::uuid>(val);
// Other approach, probably better for binary
//size_type size;
//ar(make_size_tag(size));
//for (auto it = uuid.begin(), end = uuid.end(); it != end; ++it) {
// uint8_t val;
// ar(val);
// *it = val;
//}
}
} // namespace cereal
#endif // CEREAL_TYPES_BOOST_UUID_

Answer 2

The fact that
cereal archives operate on either an std::ostream or std::istream object.
doesn't (at all) imply that it using the IO streaming operators (>>, <<). That's just the archive implementation.
You'll have to implement the free function serialize to let Cereal know about your type. You should be able to reuse the implementation shown in uuid_serialize.hpp. Chances are you should simply
move those definitions into the cereal namespace (preferrably) or into the boost::uuids namespace (might conflict in the future) for ADL to find them
best to treat the UUIDs as simple arrays of bytes (AFAIR boost::uuids::uuid is a POD data type)