From: Robert Ramey (ramey_at_[hidden])
Date: 2006-08-07 13:18:04
Guy Létourneau wrote:
> Hello Robert,
>
> Sorry for not giving you feedback earlier, I was on vacation. I've
> included your proposed changes in my test application but I still get
> the same compile error:
>
> C:/Boost/include/boost-1_33_1/boost/archive/detail/oserializer.hpp:
> In function `void boost::archive::save(Archive&, T&) [with Archive =
> boost::archive::text_oarchive, T = const A*]':
> C:/Boost/include/boost-1_33_1/boost/archive/basic_text_oarchive.hpp:78:
> instantiated from `void
> boost::archive::basic_text_oarchive<Archive>::save_override(T&, int)
> [with T = const A*, Archive = boost::archive::text_oarchive]'
> C:/Boost/include/boost-1_33_1/boost/archive/detail/interface_oarchive.hpp:78:
> instantiated from `Archive&
> boost::archive::detail::interface_oarchive<Archive>::operator<<(T&)
> [with T = const A*, Archive = boost::archive::text_oarchive]'
> ../main.cpp:101: instantiated from here
> C:/Boost/include/boost-1_33_1/boost/archive/detail/oserializer.hpp:567:
> error: incomplete type `boost::STATIC_ASSERTION_FAILURE<false>' does
> not have member `value'
> make: *** [main.o] Error 1
>
> Could you tell me what I'm missing?
>
> Thanks again for your help,
>
> Guy Letourneau
>
>
> Test application:
>
> #include <iostream>
> #include <fstream>
>
> #include <boost/archive/text_oarchive.hpp>
> #include <boost/archive/text_iarchive.hpp>
> #include <boost/serialization/export.hpp>
>
> class A
> {
> public:
>
> A()
> {
> i = 1;
> };
>
> virtual ~A()
> {
> };
>
> virtual void Dummy() = 0;
>
> private:
>
> int i;
>
> friend
> class boost::serialization::access;
>
> template <class Archive>
> void serialize( Archive& ar, const unsigned int version )
> {
> std::cout << "Serialization of A" << std::endl;
> std::cout.flush();
> }
> };
> BOOST_IS_ABSTRACT(A)
>
>
> class B : public A
> {
> public:
>
> B()
> {
> };
>
> virtual ~B()
> {
> };
>
> void Dummy()
> {
> };
>
> void SetValue( std::string& value )
> {
> Data = value;
> }
>
> private:
>
> friend
> class boost::serialization::access;
>
> template <class Archive>
> void serialize( Archive& ar, const unsigned int version )
> {
> ar & boost::serialization::base_object<A>( *this );
> ar & Data;
> std::cout << "Serialization of B" << std::endl;
> std::cout.flush();
> }
>
> std::string Data;
> };
> BOOST_CLASS_EXPORT(B)
>
>
> int main()
> {
> // Create a B object
> B* Child = new B;
>
> // Set some data
> std::string Data = "test";
> Child->SetValue( Data );
>
> // Assign it to a A ptr
****
// > const A* Parent = Child; // Parent is now const
// nope- Parent is not const - it points to a const A - not the same thing
!!!
// try
const A * const Parent = Child; // const pointer to a const A
// also the following will work - I believe
A * const Parent = Child;
>
> // create and open a character archive for output
> std::ofstream ofs( "filename" );
>
> // save data to archive
> {
> try
> {
> boost::archive::text_oarchive oa( ofs );
> // write class instance to archive
> oa << Parent; // Ptr dereferencing is performed by the
> library }
> catch( boost::archive::archive_exception& e )
> {
> std::cout << "Save failed! : " << e.what();
> std::cout.flush();
>
> return false;
> }
> catch( ... )
> {
> std::cerr << "Unknown Exception " << std::endl;
>
> return false;
> }
>
> // archive and stream closed when destructors are called
> }
>
> delete Child;
> }
>
> -----Original Message-----
> From: boost-users-bounces_at_[hidden]
> [mailto:boost-users-bounces_at_[hidden]] On Behalf Of Robert
> Ramey
> Sent: Saturday, July 22, 2006 6:43 PM
> To: boost-users_at_[hidden]
> Subject: Re: [Boost-users] [Serialization] Problem
> serializingviabaseclassptr
>
> Three show stopping problems in this code:
>
> a) A doesn't have serialize method even though
> such a method is invoked by base object. see:
> http://www.boost.org/libs/serialization/doc/serialization.html
>
> b) saving a non-const object - see rationale section
>
> c) Main show stopper:
>
>> int main()
>> {
>> // Create a B object
>> B* Child = new B;
>>
>> // Set some data
>> std::string Data = "test";
>> Child->SetValue( Data );
>>
>> // Assign it to a A ptr
>> // const A* Parent = Child; // ****** note new const - see
>> rationale
>>
>> // create and open a character archive for output
>> std::ofstream ofs( "filename" );
>>
>> // save data to archive
>> {
>> try
>> {
>> boost::archive::text_oarchive oa( ofs );
>> // write class instance to archive
> // *** big problem here. Dereferecing pointer to A
> yields a
> ref
> // *** to an A - regardless that ptr was a B. What you
> really want is:
> oa << Parent; // *** let serialization handle
> dererencing // *** instead of:
>> //oa << *Parent;
>> }
>> catch( boost::archive::archive_exception& e )
>> {
>> std::cout << "Save failed! : " << e.what();
>> std::cout.flush();
>>
>> return false;
>> }
>> catch( ... )
>> {
>> std::cerr << "Unknown Exception " << std::endl;
>>
>> return false;
>> }
>>
>> // archive and stream closed when destructors are called
>> }
>>
>> delete Child;
>> }
>>
>
>
>
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