Re: [Boost-users] [Serialization] shared_ptr to const object

Subject: Re: [Boost-users] [Serialization] shared_ptr to const object
From: elizabeta petreska (elizabeta.petreska_at_[hidden])
Date: 2009-12-20 07:05:10

Thank you for the reply.
This works!!! , but it creates a temporary. I was thinking how to cast the
constness away, without making temporary object. I gess know at least I have
one possible solution, althgough not complete happy with it :)

On 12/19/09, Steven Watanabe <watanabesj_at_[hidden]> wrote:
>
> AMDG
>
> elizabeta petreska wrote:
>
>> How to serialize shared_ptr member which points to const object.
>> The following compiles, but is not working i.e the restored
>> boost_shared_ptr  does not point to anything.
>> I tried to use const_pointer_cast to cast the const away. I suspect that
>> this is the problematic part.
>>
>> I think the question here is , how should I cast away the const correctly
>> for boost::shared_ptr<const T>?
>>
>>
>
> The problem is that you are creating a temporary when
> you do the cast.  When you deserialize, the temporary
> is modified, instead of mac.  The following seems to
> work.
>
> #include <boost/archive/xml_iarchive.hpp>
> #include <boost/archive/xml_oarchive.hpp>
> #include <boost/serialization/nvp.hpp>
> #include <boost/serialization/utility.hpp>
> #include <fstream>
> #include <boost/serialization/shared_ptr.hpp>
>
> class B
> {
> public:
>   B()  {  }
>   B(int a):ma(a)  {  }
>
>   int ma;
>
>   template<class Archive>
>   void serialize(Archive & ar, const unsigned int
>       /*version*/)
>   {
>       using boost::serialization::make_nvp;
>       ar & make_nvp("ma",ma);
>   }
> };
>
> class BC
> {
> public:
>   BC() { }
>   BC(boost::shared_ptr<B>& t):mac(t) { }
>
>   boost::shared_ptr<const B> mac;
>
>   BOOST_SERIALIZATION_SPLIT_MEMBER()
>
>   template<class Archive>
>   void save(Archive & ar, const unsigned int /*version*/) const
>   {
>       using boost::serialization::make_nvp;
>       ar & make_nvp("mac", mac);
>   }
>   template<class Archive>
>   void load(Archive & ar, const unsigned int /*version*/)
>   {
>       using boost::serialization::make_nvp;
>       boost::shared_ptr<B> temp;
>       ar & make_nvp("mac", test);
>       mac = temp;
>   }
> };
>
> int main()
> {
>   std::ofstream ofs(L"C:\\MyTest.xml");
>   std::ifstream ifs(L"C:\\MyTest.xml");
>
>   boost::shared_ptr<B> bb(new B(4));
>
>   BC aa(bb);
>
>   {
>       boost::archive::xml_oarchive oa(ofs);
>       oa & BOOST_SERIALIZATION_NVP(aa);
>   }
>
>   BC raa;
>   {
>       boost::archive::xml_iarchive ia(ifs);
>       ia & BOOST_SERIALIZATION_NVP(raa);
>   }
>
> }
>
> In Christ,
> Steven Watanabe
>
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