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Understanding Inheritance and Polymorphism in CS250

Dive into the world of inheritance and polymorphism in CS250, exploring topics such as class creation, constructor and destructor order, virtual functions, dynamic binding, and practical examples.

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Understanding Inheritance and Polymorphism in CS250

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  1. Inheritance and Polymorphism CS250 Introduction to Computer Science II

  2. Three-Level Inheritance • How would we create class Cylinder that inherits from class Circle? • In what order are the constructors called when we create an object of type Cylinder? • In what order are the destructors called? CS250 Introduction to Computer Science II

  3. Inheritance • This ends our discussion of inheritance • We have completed chapter 9 CS250 Introduction to Computer Science II

  4. Polymorphism • Program in the general, rather than program in the specific • Two underlying technologies • Virtual functions • Dynamic binding CS250 Introduction to Computer Science II

  5. Polymorphism in Action • The example we will use will utilize the point/circle classes we created earlier • For the print member function in class Circle we had the statement • Point::print(); • Why was it necessary to include Point::? • What would happen if we removed Point::? CS250 Introduction to Computer Science II

  6. Polymorphism in Action • Write the statements needed to create objects of type Circle and Point • Call the member function print on these objects • What is the output? • Create a pointer to a Point object • Create a pointer to a Circle object CS250 Introduction to Computer Science II

  7. Polymorphism • Assign the pointer to a Point object to the Point object created earlier • Assign the pointer to a Circle object to the Circle object created earlier • Invoke the print member function on both of these pointers • What is the output? CS250 Introduction to Computer Science II

  8. Polymorphism in Action • Point the pointer to a Point object to a Circle object • Is this possible? • Why? • Invoke the print member function using this pointer • What is the output? CS250 Introduction to Computer Science II

  9. Polymorphism in Action • Assigning the address of a derived class object to a base class pointer is allowed • The derived class is an object of its base class • However the functions of the base class will be invoked rather than the members of the derived class CS250 Introduction to Computer Science II

  10. Derived & Base Class Pointers • Point the pointer to a Circle object to a Point object • Is this possible? • Why? CS250 Introduction to Computer Science II

  11. Derived & Base Class Pointers • The compiler does not allow you to assign a base class object to a derived class pointer • Imagine if we could assign a Circle pointer to a Point object • What would happen if we invoked the setRadius member function? CS250 Introduction to Computer Science II

  12. Summary • We discussed the basics of polymorphism • Next time we will talk about virtual functions • We covered: • Pages 663 - 672 CS250 Introduction to Computer Science II

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