Navigating C++ and Object-Oriented Design

10.11. Template Nested Classes

“Nested Classes” on page 250 shows how nontemplate classes nest other nontemplate classes. Here's the nesting format with templates.

template <class TYPE> 
class Outer {                  // enclosing class
   . . .
   class Inner {               // enclosed class (nested)
      . . .
   };
   . . .
};

Nested classes improve encapsulation by hiding the visibility of enclosed classes. Class Inner may be a nontemplate class or a template class. This implies that only one-to-one relationships hold between nested classes and template classes. It's also possible to specify nested member template functions, which we will look at later on (see “Member Templates” on page 456).

Here's an example of nesting template classes.

 template <class TYPE> class Scheduler { // enclosing ...