Inheritance

Learning Outcomes
 Introduction
 Defining Inheritance
 Need of Inheritance
 Visibility mode
 Types of Inheritance
 Virtual Base Classes
2

Introduction
Inheritance
 OOP makes it possible to create full reusable applications
with less code and shorter development time.
 Inheritance is another important aspect of object-oriented
programming.
 In C++, it is possible to inherit attributes and methods
from one class to another.
3

Inheritance
Inheritance:
 Inheritance is the capability of one class to inherit
properties from another class.
 Base Class:
 It is the class whose properties are inherited by another
class.
 It is also called Super class.
 Derived Class:
 The class inherits the properties from base class.
 It is also called Sub class
4

Inheritance
Need of Inheritance:
 If we use the code of X even in Y without rewriting it, then
class Y inherits all the properties of X.
 Suppose if we use direct option without using inheritance, it
has following problems.
 Code written in X is repeated again in Y which leads to unnecessary
wastage of memory.
 Testing to be done separately for both class X and class Y leads to
waste of time.
 The above problem can be solved by using the concept of
inheritance.
5

Inheritance
Advantages of Inheritance:
 Reusing existing code
 Faster development time
 Easy to maintain
 Easy to extend
 Memory Utilization
Disadvantage of Inheritance:
 Inappropriate use of inheritance makes programs more
complicated.
 Calling member functions using objects creates more
compiler overheads.
6

Inheritance
Defining Derived Classes:
 A derived class is a composite class – it inherits
members from the base class and adds member of its
own.
 Syntax given below.
class D_class_name : Visib_Mode B_class_name
 Here,
 class → Keyword
 D_class_name → Name of the derived class
 :→ Shows the derivation from the base class.
 Visib_Mode → Specifies the type of derivation
 B_class_name → Name of the base class.
7

Inheritance
Visibility mode:
 The private data of base class cannot be inherited.
 Visibility mode can be:
 Private
 Protected
 Public
8

Visibility mode
Public mode:
 If inheritance is done in Public mode:
 Public members of the base class become the public
member of derived class
 Protected member of base class become the protected
member of derived class.
9
// Sub class inheriting from Base Class(Parent)
class Child : public Parent
{
public:
int id_c;
};

Visibility mode
Private mode:
 If inheritance is done in a Private mode:
 Public members of base class become the private
members of derived class.
 Protected members of base class become the private
members of derived class.
10
class Child : private Parent
{
public:
int id_c;
};

Visibility mode
Protected mode:
 If inheritance is done in a Protected mode:
 Public members of base class become the Protected members
of the base class.
 Protected members of base class become the Protected
members of the base class.
11
class Child : protected Parent
{
public:
int id_c;
};

Types of Inheritance
Types of Inheritance are:
 Based on the relationship, inheritance can be classified
into five forms:
 Single Inheritance
 Multiple Inheritance
 Multilevel Inheritance
 Hierarchical Inheritance
 Hybrid Inheritance
12

Single Inheritance:
 Single Inheritance is the process of creating a new class from
existing class base class.
 In single inheritance, a class is allowed to inherit from only
one class. i.e. one sub class is inherited by one base class only.
 Syntax:
class Base_Class
{ ………..};
class Derived_class : public Base_calss
{ ……. };
13

Multiple Inheritance:
 Multiple Inheritance is a feature of C++ where a class can
inherit from more than one classes.
 One sub class is inherited from more than one base classes.
 Syntax:
class B
{ ………..};
class C
{ ………..};
class A : public B, public C
{ ……. };
14

Multilevel Inheritance:
 In this type of inheritance, a derived class is created from
another derived class.
 Derivation of a class from another derived class is called
multilevel inheritance.
 Syntax:
class C
{ ………..};
class B: public C
{ ………..};
class A : public B
{ ……. };
15

Hierarchical Inheritance:
 If a number of classes are derived from a single base class, it is
called as hierarchical inheritance.
 Hierarchical model exhibits top down approach by breaking up
a complex class into simpler class.
 Syntax:
class B
{ ………..};
class C: public B
{ ………..};
class A : public B
{ ……. };
16

Hybrid (Virtual) Inheritance:
 Hybrid Inheritance is implemented by combining more than
one type of inheritance.
 Hybrid Inheritance is combination of Hierarchical and
multilevel inheritance.
 Syntax:
class A
{ ………..};
class B: virtual public A
{ ………..};
class C : virtual public A
{ ……. };
class D : public B, public C
{ ……. }; 17

Virtual Base Classes
Virtual Base Classes:
 A derived class with two base classes and these two base
classes have one common base class is called multipath
inheritance. An ambiguity can arise in this type of inheritance.
Such a base class is known as virtual base class.
 This can be achieved by preceding the base class name with
the word virtual.
18
class A
{ ………..};
class B: virtual public A
{ ………..};
class C : virtual public A
{ ……. };
class D : public B, public C
{ ……. };

Constructors
Constructor and Destructors in derived classes:
 If we inherit a class from another class and create an object of
the derived class:
 The constructor of base class is called first to initialize all the inherited
members.
 Destructors in C++ are called in the opposite order of that of
Constructors
19

Constructors
 Program to illustrate the use of destructors in C++.
20
class Base
{
public:
Base( ); //Default constructor
{
cout<<”Inside Base Constructor”;
}
~ Base( ); //Destructor
{
cout<<”Inside Base Destructor”;
}
};
class Derived : public Base
{
public:
Derived( ); //Default constructor
{
cout<<”Inside Derived Constructor”;
}
~ Derived( ); //Destructor
{
cout<<”Inside Derived Destructor”;
}
};
void main( )
{
Derived x;
a.display( );
}

Discussion
Questions:
 What is Inheritance? Explain any two types of Inheritance.
 What are visibility modes? Explain.
 What is the difference between public, private and protected
access specifiers?
 Explain single inheritance with a suitable C++ program.
 What is Multilevel Inheritance? Explain with a suitable
program example.
 What is virtual base class? Give example.
 What are the advantages of Inheritance?
21

Inheritance

More Related Content

What's hot

Similar to Inheritance

More from Prof. Dr. K. Adisesha

Recently uploaded

Inheritance