c++Inheritance.pdf

INHERITANCE in C++
BY,
Ranjana Thakuria
Assistant Professor,
Department of CSE, SVCE Bengaluru

HAPPY BIRTH DAY
INHERITANCE & Birthday Cake
Ranjana Thakuria, CSE Department

INHERITANCE-Example
Children inherits property (genetic
characteristics ) from their parents

INHERITANCE
 The capability of a class to derive properties and characteristics from another
class.
 New classes are created from the existing classes.
 Reusability can be achieved through inheritance.
 The new class created is called derived class or child class or Sub Class
 The existing class is known as the base class or parent class or Super class.
 The derived class now is said to be inherited from the base class.

INHERITANCE & Birthday Cake
BASE
DERIVED FROM BASE

When to use inheritance?
BASE CLASS
DERIVED CLASSes
INHERITANCE

Implementing Inheritance in C++:
Syntax:
class <derived_class_name> : <access-specifier> <base_class_name> {
//body
}
keyword to create a new class
name of the base class
Public/
Private/
Protected;
private by default
new class name, which will
inherit the base class
Example:
class B: protected A{
………
};

Implementing Inheritance
 Example:
class A{
int a;
………..
};
class B: protected A{
int b;
………
};
A
A
B
B
Does not inherit a full parent object

Implementing Inheritance
 Accessibility:
class A{
private:
int x;
protacted:
int y;
public:
int z;
};
class derived: A{
//y, z accessible
};
class general{
// z accessible
};

Modes of Inheritance
Public Mode: If derive a subclass from a public base class,
public members public
protected members protected
Protected Mode: If we derive a subclass from a Protected base class
public member  protected
protected members protected
Private Mode:
public member  private
protected members  private
A derived class doesn’t inherit access
to private data members.
class ABC : private XYZ
{ };
Or
class ABC: XYZ
{ }
class ABC : protected XYZ
{ };
class ABC : public XYZ
{ };

Mode-wise accessibility table

Example: public Derivation Accessibility
class A
{
private:
int a;
protected:
int b;
public:
int c;
};
class B: public A
{
public:
void set()
{
//a=1; //not allowed
b=2; //accessible in further derivation only
c=3; //accessible in further derivation and others
}
};
main()
{
B obj;
//obj.a=1//not allowed
//obj.b=2;//not allowed
obj.c=3;
return 0;
}

Ex: protected Derivation Accessibility
class A
{
private:
int a;
protected:
int b;
public:
int c;
};
class B: protected A
{
public:
void set()
{
b=2; //accessible in further derivation only
c=3; //accessible in further derivation only
}
};
main()
{
B obj;
//obj.c=3 ;//not allowed
return 0;
}

Ex: private Derivation Accessibility
class A
{
private:
int a;
protected:
int b;
public:
int c;
};
class B: private A
{
public:
void set()
{
b=2; //not accessible in further derivation
c=3; //not accessible in further derivation
}
};
main()
{
B obj;
//obj.c=3 ;//not allowed
return 0;
}

Types of Inheritances in C++
1. Single inheritance:
3. Multilevel inheritance:
5.Hybrid inheritance:
2. Multiple inheritance:
4. Hierarchical inheritance:
Five Types of Inheritances:

Single Inheritance:
 A class is allowed to inherit from only one class.
 Syntax:
class subclass_name : access_mode base_class {
// body of subclass
};
 Example:
class A { ... .. ...
};
class B: public A {
... .. ...
};

Single Inheritance- Example :
class A
{
protected:
int a;
public:
void set_A(int x) {
a=x;
}
void disp_A() {
cout<<endl<<"Value of A="<<a;
}
};
class B: public A
{
int b;
public:
void set_B(int x, int y) {
set_A(x);
b=y;
}
void disp_B() {
disp_A();
cout<<endl<<"Value of B="<<b;
}
};
main()
{
B b;
b.set_B(5,10);
b.disp_B();
return 0;
}
OUTPUT
Value of A=5
Value of B=10

Multiple Inheritance:
 A class can inherit from more than one class.
 i.e one subclass is inherited from more than one base class.
Syntax:
class subclass_name : access_mode1 base_class1, access_mode2 base_class2 {
// body of subclass
};

Multiple Inheritance:
 Example:
class A { ... .. ...
};
class B { ... .. ...
};
class C: public A, protected B {
... .. ...
};

Multiple Inheritance- Example :
// first base class
class Vehicle {
public:
Vehicle() { cout << "This is a Vehiclen"; }
};
// second base class
class FourWheeler {
public:
FourWheeler(){
cout << "This is a 4 wheeler Vehiclen";
}
};
// sub class derived from two base classes
class Car : public Vehicle, public FourWheeler {
public:
Car(){cout<<"nConstructed Car";}
};
// main function
int main()
{
// Creating object of sub class will
// invoke the constructor of base classes.
Car obj;
return 0;
}
OUTPUT
This is a Vehicle
This is a 4 wheeler Vehicle
Constructed Car

MultiLevel Inheritance:
 A class is derived from another derived
class.
 or one subclass is inherited from
another sub class.
 i.e, two levels of single inheritance

 Example:
class A {
... .. ...
};
class B : public A {
... .. ...
};
class C: protected B {
... .. ...
};

Example:
#include<iostream>
using namespace std;
class A
{
protected:
int a;
public:
void set_A(){
cout<<"Enter the Value of A=";
cin>>a;
}
void disp_A(){
cout<<endl<<"Value of A="<<a;
}
};
class B: public A
{
protected:
int b;
public:
void set_B()
{
cout<<"Enter the Value of B=";
cin>>b;
}
void disp_B()
{
cout<<endl<<"Value of B="<<b;
}
};
class C: public B
{
int c,p;
public:
void set_C()
{
cout<<"Enter the Value of C=";
cin>>c;
}
void disp_C()
{
cout<<endl<<"Value of C="<<c;
}
void cal_product()
{
p=a*b*c;
cout<<endl<<"Product of "<<a<<" * "<<b<<" *
"<<c<<" = "<<p;
}
};
main()
{
C _c;
_c.set_A();
_c.set_B();
_c.set_C();
_c.disp_A();
_c.disp_B();
_c.disp_C();
_c.cal_product();
return 0;
}
OUTPUT:
Value of A=10
Value of B=20
Value of C=30
Product of 10 * 20 * 30 = 6000

Hierarchical Inheritance:
 More than one subclass is inherited from a single base class.
 i.e. more than one derived class is created from a single base class.

 Example:
class B {
... .. ...
};
class A : public B {
... .. ...
};
class C: protected B {
... .. ...
};

 Example:
// base class
class Vehicle {
public:
};
// first sub class
class Car : public Vehicle {
};
// second sub class
class Bus : public Vehicle {
};
// main function
int main()
{
// invoke the constructor of base class.
Car obj1;
Bus obj2;
return 0;
}
Output
This is a Vehicle
This is a Vehicle

Hybrid Inheritance:
 Implemented by combining more than one type of inheritance.
 Example: Combining Hierarchical inheritance and Multiple Inheritance.
 Below image shows the combination of hierarchical and multiple inheritances:

Hybrid Inheritance:
Example:
// C++ program for Hybrid Inheritance
#include <iostream>
using namespace std;
// base class
class Vehicle {
public:
};
// base class
class Fare {
public:
Fare() { cout << "Fare of Vehiclen"; }
};
// first sub class
class Car : public Vehicle {
};
// second sub class
class Bus : public Vehicle, public Fare {
};
// main function
int main()
{
// invoke the constructor of base class.
Bus obj2;
return 0;
}
OUTPUT:
This is a Vehicle
Fare of Vehicle

Multipath inheritance:
 A special case of hybrid inheritance:
 A derived class with two base classes and these two base classes have one
common base class .
 Ambiguity can arise in this type of inheritance.
 Ambiguity can be resolved in two ways:
 using scope resolution operator
 using virtual base class

Multipath Ambiguity resolve:
 Avoiding ambiguity using the scope resolution operator:
obj.ClassB::a = 10; // Statement 3
obj.ClassC::a = 100; // Statement 4

Multipath Ambiguity resolve:
2) Avoiding ambiguity using the virtual base class:
Class-D has only one copy of ClassA
class ClassA{
public:
int a;
};
class ClassB : virtual public ClassA{
public:
int b;
};
class ClassC : virtual public ClassA{
public:
int c;
};
class ClassD : public ClassB, public ClasC{
public:
int d;
};
int main()
{
ClassD obj;
obj.a = 10; // Statement 3
obj.a = 100; // Statement 4
obj.b = 20;
obj.c = 30;
obj.d = 40;
cout << "n a : " << obj.a;
cout << "n b : " << obj.b;
cout << "n c : " << obj.c;
cout << "n d : " << obj.d << 'n';
}

Inheritance and Constructors:
 Constructors can be inherited.
 The constructors of inherited classes are called in the same order in which
they are inherited.
Example Constructors in inheritance:
class A {
A(){}
... .. ...
};
class B: public A {
B():A(){}
... .. ...
};

Order of Inheritance- Constructors :
class A1{
public:
A1(){
cout << "Constructor of the base class A1 n";
}
};
class A2{
public:
A2(){
cout << "Constructor of the base class A2 n";
}
}; 3 1 2
class S: public A1, virtual A2
{
public:
S(): A1(), A2(){
cout << "Constructor of the derived class S n";
}
};
// Driver code
int main()
{
S obj;
return 0;
}

THANK YOU

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