[Boost-Users] Re: shared_ptr and inheritance

From: Jon Kalb (kalb_at_[hidden])
Date: 2001-12-09 20:50:46

At 12:06 AM +0000 12/10/01, rz0 wrote:
>--- In Boost-Users_at_y..., Jon Kalb <kalb_at_L...> wrote:
>>  At 2:56 AM +0000 12/9/01, rz0 wrote:
>>  >#include <iostream>
>>  >#include <boost/smart_ptr.hpp>
>>  >
>>  >class A
>>  >{
>>  >public:
>>  >  virtual void func1() { std::cout << "A::func1" << std::endl; }
>>  >};
>>  >
>>  >class B : public A
>>  >{
>>  >public:
>>  >  void func1() { std::cout << "B::func1" << std::endl; }
>>  >  void funcB() { std::cout << "B::funcB" << std::endl; }
>>  >};
>>  >
>>  >class C : public A
>>  >{
>>  >public:
>>  >  void func1() { std::cout << "C::func1" << std::endl; }
>>  >  void funcC() { std::cout << "C::funcB" << std::endl; }
>>  >};
>>  >
>>  >class Holder
>>  >{
>>  >  boost::shared_ptr<A> aptr;
>>  >public:
>>  >  void setclass(boost::shared_ptr<A> a) { aptr = a; }
>>  >  void callfunc() { aptr->func1(); }
>>  >};
>>  >
>>  >int main()
>>  >{
>>  >
>>  >  Holder holder;
>>  >
>>  >  boost::shared_ptr<B> b(new B());
>>  >  boost::shared_ptr<C> c(new C());   
>>  >
>>  >  holder.setclass(b);    //<-------
>>  >  holder.setclass(c);    //<-------
>>  >
>>  >  holder.callfunc();
>>  >
>>  >return 0;
>>  >}
>>  >
>>  >VC++ 6.0 flags the above lines with a conversion error.
>>  >
>>  >Is there any way to resolve this?
>>
>>  Can you just define b and c as boost::shared_ptr<A>?
>
>Hi Jon
>
>Thank you very much for the response.  Unfortunately this will cause
>the same problem that I ran into with std::auto_ptr and that is
>methods funcB and funcC which are exclusive to B and C are not
>allowed to be called.

Your original code worked for me, but I'm using CodeWarrior. I 
noticed that the function that you want to have called:

      template<typename Y> shared_ptr(const shared_ptr<Y>&);

is #ifdef'ed on BOOST_MSVC6_MEMBER_TEMPLATES, but I don't know what 
that define means.
--
Jon Kalb
Kalb_at_[hidden]