Re: [Boost-users] [serialization] [units] class_id and class_name to describe quantity dimension in serilization archive

Subject: Re: [Boost-users] [serialization] [units] class_id and class_name to describe quantity dimension in serilization archive
From: Robert Ramey (ramey_at_[hidden])
Date: 2011-09-25 12:59:24

Alfredo Correa wrote:
> Hi François,

>> Rather than acking the BS lib, what you asked for could be probably
>> easily implemented by some specific I/O manager dedicated for your
>> specific need during I/O operations.
>
> the "hacking" I suggested (i.e. the explicit code) does not hack
> Boost.Serialization but it hacks Boost.Units.serialization, and it is
> within the framework of Boost.Serialization. (the standalone
> serialization/load/save function can be anything the user wants... I
> guess, although I was not sure if it should throw or not)

FYI, the serialization library doesn't impose any requirments as to
how any particular type should be serialized, other than the
the requirement that the save/load be symetric.  So if you want
to make you're own implementation of the serialization of the
units library it's just fine.  Just put it in to a separate header

../correat/serialization/units.hpp

and you're in business.

>> When I serialize some heterogeneous sets of objects
>> in any kind of archives (text/XML/eos::portable_binary), I first
>> store/load a "serialization tag" (std::string) that identifies the
>> type/class of the next object to be stored|loaded. It is thus my
>> responsability to manage a set of known tags associated to the
>> classes I need to serialize.

hmm - I just use variant with all the possible types and just
serialize that - which is already in boost.  Also serialization
of a pointer through the base class addresses this issue
in other contexts.

>
> Do you mean something like this?
>
> void serialize(Archive & ar, Object obj,  unsigned){
>   ar & typeof(obj.a).name();  // just one way to store type
> information, check enforce can be added in the same way I did in my
> quantity example
>   ar & obj.a;
>   ar & "type of b";  // just one way to store type information
>   ar & obj.b;
> }

My preference is more something like

ar & boost::variant<....>(a)
...

But not to handle a pointer to an "a" would require usage of 
"set_object_address"
call (hack) to work.

So basically, your problem is too many options that you have to look at.

Robert Ramey