Re: pure virtual template...

From:

mathieu <mathieu.malaterre@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 26 Oct 2007 12:49:30 -0000

Message-ID:

<1193402970.735602.223830@d55g2000hsg.googlegroups.com>

On Oct 26, 2:19 pm, mathieu <mathieu.malate...@gmail.com> wrote:

Hi there,

I don't think I'll be able to describe my issue correctly, so
instead I'll just give a pseudo C++ code I am struggling with.
Basically I am looking for a 'pure virtual template' function that I
would be able to declare in the base class (*).

Hum...without much satisfaction here is my temporary solution.
Hopefully you guys will suggest something not involving making the
base class be polymorphic...

#include <iostream>

struct Base
{
  template <typename T> void foo() const;
  int base;
  virtual void bla() {}
};

struct A : public Base
{
  template <typename T> void foo() const { std::cout << "A" <<
std::endl; }
  double a;
};

struct B : public Base
{
  template <typename T> void foo() const { std::cout << "B" <<
std::endl; }
  float b;
};

template <typename T>
void Base::foo() const
{
  const A * a = dynamic_cast<const A*>(this);
  const B * b = dynamic_cast<const B*>(this);
  if( a ) a->foo<T>();
  else if( b ) b->foo<T>();
}

int main(int argc, char *argv[])
{
  Base * base;
  if( argc > 1 )
    {
    base = new A;
    }
  else
    {
    base = new B;
    }
  base->foo<int>();
  return 0;
}