C++ Primer Plus, Fourth Edition

Multiple Inheritance

Multiple inheritance (MI) describes a class that has more than one immediate base class. As with single inheritance, public multiple inheritance should express an is-a relationship. For example, if you have a Waiter class and a Singer class, you could derive a SingingWaiter class from the two:

class SingingWaiter : public Waiter, public Singer {...};

Note that you must qualify each base class with the keyword public. That's because the compiler assumes private derivation unless instructed otherwise:

class SingingWaiter : public Waiter, Singer {...}; // Singer is a private base

As discussed earlier in this chapter, private and protected MI can express a has-a relationship; the studenti.h implementation of the Student