inheritance and namespaces

Question

I am trying a my first useful object oriented program with some namespace usage. I have a base class B which is in the namespace NS. If I try to inherit from this base class to get the inheritance work, I should use the NS::B in the class decleration as below, is this really the case? Or is there a more widely accepted sytle for this inheritance syntax?

namespace NS
{
    class D: public NS::B{
    ...
    };
}

Best, Umut

Answer 1

If your D is in namespace NS, you don't have to qualify NS::B, since D and B are in the same namespace. You can just use class D : public B.

Answer 2

When you are inside of namespace NS, you don't usually⁽¹⁾ need to qualify the names of functions, classes, or other entities that are in the namespace NS. Given:

namespace NS {
    class B { };
}

the following two definitions of D are the same:

namespace NS {
    class D : public NS::B { };
}

and:

namespace NS {
    class D : public B { };
}

---

(1) Argument-Dependent Lookup (ADL) can cause some ugly issues, especially when using templates, and to fix them you may need to qualify names.