Inheritance relationship

Inheritance is the higher level relationship that can be represented directly in C++ and the one that figures largest in the early stages of a design. In practice inheritace is appearing in two forms.

• With inheritance we may collect the common set of attributes (data members) and behaviour (member functions) of related classes into a common base class. That procedure is called generalization.
• Otherwise, we may distinguish difference in data structure or in behaviour between objects of a certain classes: collecting them into different derived classes. That procedure is called specialization.

We express inheritance relationship in C++ in the following way:

class base1 { /* ... */ };
class base2 { /* ... */ };
class base3 { /* ... */ };

class derived : public base1, protected base2, private base3 { /* ... */ };

Of cource the derived class depends on its base classes. It is less often appreciated that if a class has a virtual function, the class depends on the derived classes. Similarly, if a class uses a protected member, that is again a dependency from the derived classes. Try to minimalize such dependencies.