This chapter presents the following content: Introduction to inheritance, inheritance in C++, IS-A relationship, polymorphism in inheritance, classes in inheritance, visibility rules, constructor and base class, adding members. | Lecture 14 Recap Introduction to Inheritance Inheritance in C++ IS-A Relationship Polymorphism in Inheritance Classes in Inheritance Visibility Rules Constructor and Base Class Adding Members Overriding a Method Methods can be override from the base class in the derived class by simply providing a derived class method with the same signature A derived class method must have the same or compatible return type Sometimes it is required to invoke the derived class method to the base class method to augment a base class method rather than doing something entirely different. This is known as partial overriding The scope operator can be used to call a base class method Example class Workaholic : public Worker { public : void dowork( ) { Worker::doWork( ); // Work like a Worker drinkCof fee ( ) ; // Take a break Worker::doWork( ); // Work like a Worker some more } }; Static and Dynamic Binding Example Code 1 Worker w; 2 Workaholic wh; 3 . . . 4 w. doWork ( ) ; wh. doWork ( ) ; The above code illustrates the fact that we can declare Worker and Workaholic objects in the same scope because the compiler can deduce which dowork method to apply w is a Worker and wh is a Workahol ic, so the determination of which dowork is used in the two calls at line 4 is computable at compile time The decision made at compile time about which function to use to resolve an overload static binding/overloading Example 1 Worker *wptr; 2 cin >> x; 3 if (x != 0 ) 4 wptr =new Workaholic ( ); 5 else 6 wptr= new Worker ( ); 7 8 9 wptr -> doWork ( ); //which doWork is used Explanation of Example If x is zero, we create a Worker object; otherwise, we create a Workaholic object Recall that, as a Workaholic IS-A Worker, a Workaholic can be accessed by a pointer to a Worker Any method that we might call for Worker will have a meaning for Workaholic objects Public inheritance automatically defines a type conversion from a pointer to a derived class to a pointer to the base class We can declare that wptr | Lecture 14 Recap Introduction to Inheritance Inheritance in C++ IS-A Relationship Polymorphism in Inheritance Classes in Inheritance Visibility Rules Constructor and Base Class Adding Members Overriding a Method Methods can be override from the base class in the derived class by simply providing a derived class method with the same signature A derived class method must have the same or compatible return type Sometimes it is required to invoke the derived class method to the base class method to augment a base class method rather than doing something entirely different. This is known as partial overriding The scope operator can be used to call a base class method Example class Workaholic : public Worker { public : void dowork( ) { Worker::doWork( ); // Work like a Worker drinkCof fee ( ) ; // Take a break Worker::doWork( ); // Work like a Worker some more } }; Static and Dynamic Binding Example Code 1 Worker w; 2 Workaholic wh; 3 . . . 4 w. doWork ( ) ; wh. doWork ( ) ; The above code
