Members declared by using a using declaration can be referenced by using explicit qualification. using C::g // error: C isn't a base of D2Įxample: using declaration with explicit qualification When used to declare a member, a using declaration must refer to a member of a base class. G('c') // Invokes B::g(char) instead of recursingĮxample: using declaration to declare a member Using B::g // B::g(char) is now visible as D::g(char)į('c') // Invokes B::f(char) instead of recursing Using B::f // B::f(char) is now visible as D::f(char)

Example: using declaration in class fieldĪ using declaration can be used in a class definition. The using keyword is also used for type aliases. This is in contrast to the using directive, which allows all the names in a namespace to be used without qualification. It allows a single name from a specific namespace to be used without explicit qualification in the declaration region in which it appears. RemarksĪ using declaration introduces an unqualified name as a synonym for an entity declared elsewhere. The keyword typename is optional and may be used to resolve dependent names when introduced into a class template from a base class.Īn unqualified id-expression, which may be an identifier, an overloaded operator name, a user-defined literal operator or conversion function name, a class destructor name, or a template name and argument list.Ī comma-separated list of nested-name-specifier unqualified-id declarators, followed optionally by an ellipsis. A single scope resolution operator may be used to introduce a name from the global namespace.

Syntax using nested-name-specifier unqualified-id Ī sequence of namespace, class, or enumeration names and scope resolution operators (::), terminated by a scope resolution operator. The using declaration introduces a name into the declarative region in which the using declaration appears.

Declaration synonym