Ivor Horton's Beginning Visual C++ 2012

NESTED CLASSES

You can put the definition of one class inside the definition of another, in which case, you have defined a nested class. A nested class has the appearance of being a static member of the class that encloses it and is subject to the member access specifiers, just like any other member of the class. If you place a nested class definition in the private section of a class, the class can only be referenced from within the scope of the enclosing class. If you specify a nested class as public, the class is accessible from outside the enclosing class, but the nested class name must be qualified by the outer class name in such circumstances.

A nested class has free access to all the static members of the enclosing class. All the instance members can be accessed through an object of the enclosing class type, or a pointer or reference to an object. The enclosing class can only access the public members of the nested class, but in a nested class that is private in the enclosing class, the members are frequently declared as public to provide free access to the entire nested class from functions in the enclosing class.

A nested class is particularly useful when you want to define a type that is only to be used within another type, whereupon the nested class can be declared as private. Here’s an example of that:

// A push-down stack to store CBox objects #pragma once class CBox; // Forward class declaration class CStack { private: // Defines items to store in the stack struct ...