Question

I would appreciate any help as C++ is not my primary language.

I have a template class that is derived in multiple libraries. I am trying to figure out a way to uniquely assign an id int to each derived class. I need to be able to do it from a static method though, ie.

template < class DERIVED >
class Foo
{
public:
    static int s_id()
    {
        // return id unique for DERIVED
    }
    // ...
};

Thank you!

Answer 1

Here’s what I ended up doing. If you have any feedback (pros, cons) please let me know.

template < class DERIVED >
class Foo
{
public:
    static const char* name(); // Derived classes will implement, simply

                               // returning their class name
    static int s_id()
    {
        static const int id = Id_factory::get_instance()->get_id(name());
        return id;
    }
    // ...
};

Essentially the id will be assigned after doing a string comparison rather than a pointer comparison. This is not ideal in terms of speed, but I made the id static const so it will only have to calculate once for each DERIVED.