Programming Using C++ Session 14

8/13/2019 Programming Using C++ Session 14

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Dynamic Polymorphism

NIIT Programming Using C++/Session 14/Slide 1 of 15

Objectives

In this lesson, you will learn to:

Implement the concept of bindingUse virtual functions

Use pure virtual functions to create abstract classes

Implement dynamic polymorphism by using latebinding


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Refers to any entity changing its form, depending oncircumstances


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Binding

Is the process of associating a function with a class byidentifying the type of the object or pointer that is usedto invoke the function


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Binding (Contd.)

Example:

calc_net_salary()

calc_net_salary() calc_net_salary()

Trainee Class Confirmed Class

Employee class


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Dynamic Binding

Is done during runtime

Is also called late binding


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Virtual Function

Is a function that is declared as virtual in a base classand is redefined by a derived class


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Using Virtual FunctionsExample:class Employee

{..virtual int calc_net_salary();

..};class Contract:public Employee

{..


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Using Virtual Functions (Contd.)int calc_net_salary();.

.

.};class Direct_Contract: public Contract

{..int calc_net_salary();

.

.};


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Pure Virtual Function

Is a function without a body

Is created by adding the notation =0 to the virtualfunction declaration

Example:

virtual int calc_net_salary()=0;


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Abstract Class

Is a class containing one or more pure virtualfunctions

Is used as a base class for deriving specific classesof the same kind


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Static vs Dynamic Polymorphism (Contd.)

Dynamic polymorphism

Is considered more flexibleIs based on overriding principles, which, therefore,is purely class scope and is based on inheritance


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Problem Statement 10.D.1

Create an application that:

Accepts customer details Accepts dealer details

Displays customer details

Displays dealer details


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Summary

In this lesson, you learned that:

The instances of an abstract class cannot be createdbut pointers to it can be created

A function exhibits dynamic polymorphism when itexists in more than one form, and calls to its various

forms are resolved dynamically when the program isexecuted

Static binding is considered to be more efficient whiledynamic binding is more flexible


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Summary (Contd.)

Dynamic polymorphism refers to an entity changing itsform, depending on circumstances

The virtual keyword is used to declare a function asvirtual

Virtual functions that have no body are called pure

virtual functions A class containing one or more pure virtual functionsis called an abstract class

Documents

Programming Using C++ Session 14