A class which does not need an instance

Question

Is it possible to make a class which does not need to be instantiated? In other words, is it possible to use functions of that class without having an instance of it?

Answer 1

You can use static functions, those are bound to the Class, not an instance.

class Test{
    static void 
    doSomething()
    {
        std::cout << "something" << std::endl;
    }
}

int
main(int argc, char** argv)
{
    Test::doSomething(); //prints "something" without instance of Test
}

Otherwise you could build a Singleton, in which case the class itself would hold the instance, but I am not sure if this is what you wanted to know...

Answer 2

You could make all member functions and variables static, but then one starts to wonder why it should be a class, and not a namespace.

There is a good reason, though: you may want to use a class template like this. C++14 will add variable templates, which make the same possible without a class. A class also allows access control; you can fake this for the non-template case with anonymous namespaces, but a class may be more natural.