How are member types implemented?

Question

I\'m looking at this resource:

http://www.cplusplus.com/reference/vector/vector/

For example, the iterator member type on class vector.

Woul

Answer 1

The C++ Standard does not use this phrase either. Instead, it would call it a nested type name (§9.9).

There are four ways to get one:

class C
{
public:
   typedef int int_type;       // as a nested typedef-name
   using float_type = float;   // C++11: typedef-name declared using 'using'

   class inner_type { /*...*/ };   // as a nested class or struct

   enum enum_type { one, two, three };  // nested enum (or 'enum class' in C++11)
};

Nested type names are defined in class scope, and in order to refer to them from outside that scope, name qualification is required:

int_type     a1;          // error, 'int_type' not known
C::int_type  a2;          // OK
C::enum_type a3 = C::one; // OK