Aljaz wrote:
Hey
I took a look at smart pointer example.. However, I need different approach in the following code:
spa = boost::shared_ptr<A>(new B); spa1 = spa; display(spa, spa1); // serialize it { std::ofstream ofs(filename.c_str()); boost::archive::text_oarchive oa(ofs); oa.register_type(static_cast(NULL)); oa << spa; oa << spa1; }
Do I have to register_type this way? Can I use BOOST_EXPORT .. instead?
Yes
When I want to deserialize data, the derived class will be unknown, so I have to deserialize data with base class shared pointer..
This will then contain information - type of derived class, and then I will cast it to derived class..
You may not have to do this. And you may not want to. The typical use case for using an abstract base class is to have all the functions in the derived class declared private and be called only through the the virtual function table in the abstract base class. The separates the interface defined in the abstract base class defined from the specific implementation in the derived class.
How could I do this?
a) You can embed a function in the base class like who_am_i() which returns an indictator of what kind of class it "really" is. b) you can use a function from the extended_type_info family of the serialization library to do something similar Neither of these are recommend as far as I'm concerned. The best is to make all the functions you want to call virtual and call them through the base class. This topic is addressed in Scott Meyers "Effective C++" Another effect is that you can add more derived classes without even recompiling the code you're already using. There is a demo in the serialization library which illustrates this.
Thank you very much
you're welcome Robert Ramey