Question

What does it mean to have a using inside a class definition?

class myClass {
public:
  [...]
  using anotherClass::method;
};

Answer 1

That declaration unhides a base class member. This is most often used to allow overloads of a member function. Example:

class Base {
public:
   void method() const;
};

class Derived : public Base {
public:
   void method(int n) const;
   // Without the using, you would get compile errors on d.method();
   using Base::method;
};