Question

I’m trying to use templates with multiple to pass data onto a function, but using only the first template argument as a filter. Something like this:

template <typename A, typename B>
class Component {

};

template <typename A>
class Context {
    public:
        void add(Component<A, void *> comp) {
        }
}

typedef struct Foo { int x; } Foo;
typedef struct Bar { int y; } Bar;
Context<Foo> *context = new Context<Foo>();
Component<Foo, Bar> *comp = new Component<Foo, Bar>();
context->add(comp); // error

But the compiler complains that it cannot convert Component<Foo, Bar> to Component<Foo, void *>. Is there a way to accomplish this?

Answer 1

I think what you probably need to do is change the signature of the ‘add’ method:

template <typename A>
class Context
{
public:
  template<class B>
  void add(Component<A, B> comp)
  {           
  }
};

However, I don’t know the details of your problem so this is a mere guess.