Question

I have a template class:

template<typename A, typename B>
class A {

};

---

In another .h file

template<typename A, typename B>
class A; //forward declaration

How could I declare m_A over here? I keep getting C++ forbids declaration of A with no type error:

class B {
  A* m_A;
};

Answer 1

If you don’t know the types that you want to instantiate A with when inside of B, then you will have to also make a template out of B

template<typename A1, typename B1>
class B
{
   A<A1, B1>* m_A;
};

Either that, or you would have to instantiate A as a specific type, i.e.,

class B
{
    A<Type_1, Type_2>* m_A;
};