Re: Problem with template

From:
Victor Bazarov <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Sun, 12 Oct 2008 14:59:11 -0400
Message-ID:
<gcthdu$44c$1@news.datemas.de>
lhommedumatch wrote:

I have a derived template class and I want to call a method of the
derived class from the base class.
But the method need a template parameter.
How can I do?


Make the base class a template as well, and make that function a pure
virtual function which every derived class must override.

Here is the code that doesn't work.

#include <iostream>
#include <string>

using namespace std;

//==============================================================


Add here:

   template<class T>

class A
{
   public:
   A()
   {
      std::cout << "constructeur de A" << std::endl;
   }


Add here

      virtual

   ~A()
   {
      std::cout << "destructeur de A" << std::endl;
   }


Add here:

      virtual void setValue(T) = 0;

};

//==============================================================
template <class T> class B: public A


Add here

    <T>

{
   public:
   B():A()
   {
      std::cout << "constructeur de B" << std::endl;
   }
   ~B()
   {
      std::cout << "destructeur de B" << std::endl;
   }
   T _value;
   void setValue(T p_value)
   {
    _value = p_value;
   }
};

//==============================================================
int main()
{
   A *a = new B<int>;
   a->setValue(23131);
   delete a;


If the destructor of A isn't virtual, the deletion of 'a' pointer will
have undefined behaviour.

}
//==============================================================

Thanks


YW

V
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