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Lecture note Data visualization - Chapter 14

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 note Data visualization - Chapter 14 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 Example 1 Worker wptr 2 cin gt gt x 3 if x 0 4 wptr new Workaholic 5 else 6 wptr new Worker 7 8 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 is a pointer to the base class Continued . The decision about which dowork to use can be made at compile time or at run time If the decision is made at compile time worker s dowork must be used because that is the type of wptr at compile time If wptr is actually pointing at Workaholic this