C++ Primer, Fifth Edition

protected Members

As we’ve seen, a class uses protected for those members that it is willing to share with its derived classes but wants to protect from general access. The protected specifier can be thought of as a blend of private and public:

• Like private, protected members are inaccessible to users of the class.

• Like public, protected members are accessible to members and friends of classes derived from this class.

In addition, protected has another important property:

• A derived class member or friend may access the protected members of the base class only through a derived object. The derived class has no special access to the protected members of base-class objects.

To understand this last rule, consider the following example:

class ...