1. Chapter 15 – Inheritance, Virtual Functions, and Polymorphism

2. Inheritance Name of another way in which classes and objects relate
Base class
Derived class
When object of derived class declared
Object of base class is automatically created and contained within derived class object
Lesson 15.1

3. Image of base class object creation when derived class object instantiated
Lesson 15.1

4. Defining a Base Class
class Base { private: type base_priv_dat; protected:
type base_prot_dat;
public:
type base_function_name ( ); };
Lesson 15.1

5. Defining a Derived Class
class Derived: public Base { private: int derived_priv_dat; public:
void derived_function_name ( ); };
Lesson 15.1

6. Interaction Between Base and Derived Class Objects
Private base class members are private member of base class only
Protected base class members are protected members of both derived and base classes
Public base class members are public members of derived and base classes
Derived class members convey no special access privileges to base class functions
Lesson 15.1

7. Relationship Between Base and Derived Objects
Base object
private data
private data
protected data
public functions
public functions
derived_object.derived_function( )
derived_object.base_function( )

8. No Base Class Object Name
Use only derived object name to access both derived and base class functions
Derived class takes precedence
over-riding base class function
Lesson 15.1

9. Comparison of Types of Class and Object Interactions
Client class
object
Server class
Friend class
object
Granting class
On all examples, upper boxes represent
private data members and lower boxes
represent public member functions.
Derived class
object
Base
class object
Component
class object
Composite Class
Object
Lesson 15.1

10. Private and Protected Inheritance
class Derived : private Base
public and protected members of Base become private members of Derived
private members of Base remain private to Base
class Derived : protected Base
public and protected members of Base become public and protected member of Derived
Lesson 15.1

11. Order of Constructor and Destructor Function Calls
Both base and derived constructors called when derived class object instantiated
Bass class constructor called first, derived constructor second
Derived class destructor called first, base class destructor second
Order in which objects declared determines order of constructor calls
Lesson 15.2

12. Other Uses of Inheritance
Well suited to extending or customizing existing code
Can make full use of base class features and add specific features
Can modify base classes without requiring derived classes to be modified
Allows base classes to remain up to date
Lesson 15.1

13. Explicit Call to Base Class Constructor
Derived object (value1, value2);
Derived :: Derived (type derived_var, type base_var)
:derived_member (derived_var), Base (base_var)
Constructor
Lesson 15.2

14. Effect of Inheritance Levels
Object for lowest level class contains sub-objects of all other classes
Order of calling constructors is from top down in inheritance graph
Pass data one step or level at a time
Functions can be overridden in any class down inheritance graph
Can assign derived class objects to base class objects, but not reverse
Lesson 15.3

15. Effect of Inheritance Levels
Object for lowest level class contains sub-objects of all other classes
Planet object
(no name)
Celestial_body
object
(no name)
Earth object
Lesson 15.3

16. Multiple Inheritance
Class can inherit from more than one class directly
When one class has "is a" relationship with more than one class
Lesson 15.4

17. Virtual Classes
Class which we are not allowed to create independent objects
Used as base class for other classes for which we do want independent objects
C++ automatically makes class virtual when member of class is pure virtual function
virtual type function (type, type) = 0;
Lesson 15.5

18. Pointers and Inheritance
Can declare base class type pointer variable and assign address of derived class object
Any address of object down inheritance graph
Lesson 15.5

19. Binding Association of function call with a function Early binding
Occurs during compilation
Also called static or compile-time binding
Late binding
Occurs during execution
Also called dynamic or run-time binding
Lesson 15.5

20. Polymorphism Achieved by creating and using virtual functions
Code making function call does not explicitly state which function it is calling
C++ decides during execution which is correct function

21. Summary Learned how to: Create an inheritance hierarchy
Use inheritance as a form of class interaction
Make a virtual class
Use polymorphism in an engineering program