polymorphic C++ references

Question

I was wondering how you can do polymorphism with references, as opposed to pointers.

To clarify, see the following minimal example:

cl         


        

Answer 1

Erm, is this not sufficient?

#include 

struct A;

struct B
{
  B(A& a);

  void foo();

  A& _a;
};

struct A
{
  virtual void foo() =0;
};

struct A1 : public A
{
  virtual void foo() { std::cout << "A1::foo" << std::endl; }
};

B::B(A& a) : _a(a) {}
void B::foo() { _a.foo(); }


int main(void)
{ 
  A1 a;  // instance of A1
  B b(a); // construct B with it

  b.foo();
}