C++ inheritance and function overriding

Solution 1:

The term used to describe this is "hiding", rather than "overriding". A member of a derived class will, by default, make any members of base classes with the same name inaccessible, whether or not they have the same signature. If you want to access the base class members, you can pull them into the derived class with a using declaration. In this case, add the following to class Y:

using X::spray;

Solution 2:

That's so called 'hiding': Y::spray hides X::spray. Add using directive:

class Y : public X
{
public:
   using X::spray;
   // ...
};

Solution 3:

Classes are scopes and a class scope is nested in its parent. You have exactly the same behavior with other nested scopes (namespaces, blocks).

What happen is that when the name lookup searches for the definition of a name, it looks in the current namespace, then in the englobing namespace and so on until it find one definition; the search then stop (that's without taking into account the complications introduced by argument dependent name lookup -- the part of the rules which allows to use a function defined in the namespace of one of its argument).