Robert Ramey said: (by the date of Sat, 7 Oct 2006 17:12:18 -0700)
Jeremy Pack wrote:
It is, basically, a library for building plugins.
Note the serialization library contains code which handles essentially same problem domain. Its under extended_type_info. It even has its own documentation. However some of the functionality is mixed into the serialization library.
It has the following features:
no common base class required for objects created by factory registration by GUID usage of rtti optional object don't have to be default constructible class definitons can be DLLs, - static templates refer to DLLS as necessary only if the derived class GUID is explicitly referred to.
So I have examined the extended_type_info docs, first a note about few typos there, then a real question :) 1. a typo? I can't understand this sentence in Miscellaneous/extended_type_info/features: "The first is a global type table. it and has with an entry for each type used." 2. missing A,B,C ;) in Miscellaneous/void_cast: "void_cast_register(); void_cast_register(); automatically derives the fact that A can be upcast to C and vice-versa." 3. "case studies"/shared_ptr revisited: "... of serializing a moderatly compiicated class structure. " ^^^^ ;) 4. please emphasize your example, by adding a subsection "Example" in the doc about extended_type_info. I mean, add subsection title just before: "The test program test_no_rtti implements this function in terms of the extended_type_info...." I had clicked it ( http://www.boost.org/libs/serialization/test/test_no_rtti.cpp ) the first time when I was reading from top to bottom, but later I couldn't find it, as I did not remember where I clicked :) 5. if I use extended_type_info with rtti, will my binary files be portable between various platforms? (I assume that without rtti they will be) 6. a bit related question: does binary serialization take care of endianess and different sizes of fundamentals across various platforms? (size in bytes) Type ia32 PowerPC amd64 ----------------------------------- long 4 4 8 unsigned long 4 4 8 long double 12 8 16 7. the real question: is it possible to use extended_type_info for the class factory purposes without actually using serialization, for example like that below (with or without rtti). It's just your example, slightly modified: class polymorphic_base { friend class boost::serialization::access; template<class Archive> void serialize(Archive & /* ar */, const unsigned int /* file_version */){ } public: virtual const char * get_key() const = 0; virtual ~polymorphic_base(){}; }; BOOST_IS_ABSTRACT(polymorphic_base) BOOST_CLASS_TYPE_INFO( polymorphic_base, extended_type_info_no_rtti<polymorphic_base> ) // note: types which use ...no_rtti MUST be exported BOOST_CLASS_EXPORT(polymorphic_base) class polymorphic_derived1 : public polymorphic_base { friend class boost::serialization::access; template<class Archive> void serialize(Archive &ar, const unsigned int /* file_version */){ ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(polymorphic_base); } public: virtual const char * get_key() const ; }; BOOST_CLASS_TYPE_INFO( polymorphic_derived1, extended_type_info_no_rtti<polymorphic_derived1> ) BOOST_CLASS_EXPORT(polymorphic_derived1) const char * polymorphic_derived1::get_key() const { const boost::serialization::extended_type_info *eti = boost::serialization::type_info_implementation<polymorphic_derived1> ::type::get_instance(); return eti->get_key(); } int main( int /* argc */, char* /* argv */[] ) { // the most important line: // this function takes 'const char* class_name' (or GUID ?) as an argument. polymorphic_base* p=please_somehow__create_an_instance_of("polymorphic_derived1"); } -- Janek Kozicki |