Re: [Boost-users] Serializing of object with map and multimap. Questions.

Subject: Re: [Boost-users] Serializing of object with map and multimap. Questions.
From: Jeff Flinn (TriumphSprint2000_at_[hidden])
Date: 2009-11-05 08:12:16

B Hart wrote:
> I've been having some problems storing and loading a class with a map 
> and a multimap.  The map contains values that are simple objects of 
> another class.  My questions are below.  Here is also a link to the same 
> question posted on stackoverflow.
> Thanks.
> 
> http://stackoverflow.com/questions/1676781/boost-serializing-of-object-containing-map-with-object-values-and-multimap-wit
> 
> See below a main() and two very simple classes. Then per Boost 
> serialization (and what is shown) my questions are:
> 
> 1) Does class B need the normal overloaded stream insertion operators 
> '<<' and '>>' to be defined? Currently in my real code it doesn't have 
> these.

As stated in: 
http://www.boost.org/doc/libs/1_40_0/libs/serialization/doc/tutorial.html#simplecase

you provide a template member function:

    friend class boost::serialization::access;

    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)

or non-intrusively: 
http://www.boost.org/doc/libs/1_40_0/libs/serialization/doc/tutorial.html#nonintrusiveversion

    namespace boost {
    namespace serialization {

    template<class Archive>
    void serialize(Archive & ar, gps_B& b, const unsigned int version)

> 2) Does class A in the store() and load() methods need to iterate 
> through the map and multimap containers explicitly, storing/loading 
> their key:value pairs explicitely? e.g. something like:
> 
> I assume that I don't need to do this, but am not certain.

As in: 
http://www.boost.org/doc/libs/1_40_0/libs/serialization/doc/tutorial.html#stl

    #include <boost/serialization/list.hpp>

     std::list<bus_stop> stops;
     template<class Archive>
     void serialize(Archive & ar, const unsigned int version)
     {
         ar & stops;
     }

Just replace list above with map/multimap.

> 3) Assuming class B has only the two data members shown, does it need a 
> default constructor included explicitly? (as opposed to the implicit 
> default constructor)

Not a serialization issues, but what if you ever default construct a B 
and use it, what state do you want it in?

> 4) Does B need to have an overide for the comparison operator '>'? I 
> assume that it doesn't since this is a very simple class.

Not sure what this has to do with serialization.

Jeff