Inheritance is one of the
most important feature of Object Oriented Programming System(OOPs). A
class to derive the properties and characteristics from another class is
called Inheritance. That means the child class to acquire the properties
(the data members and the member functions) of parent class.
Child Class:
A class that inherits
properties from another class is known as child class, it is also known as
derived class or subclass.
Parent
Class:
The class whose properties are
inherited by other class is known as parent class, super class or base class.
The
advantages of using inheritance in C++
The main advantages of
inheritance are code reusability and readability.
When child class inherits the properties and
functionality of parent class, we need not to write the same code again in
child class.
This makes it easier to reuse the code and
the code becomes much more readable
Let’s
take a real life example to understand this:
Consider a group of
vehicles. You need to create classes for Bus, Car and Truck.The methods
fuelAmount(), capacity(), applyBrakes() will be same for all of the three
classes. If we create these classes avoiding inheritance then we have to write
all of these functions
Not used inheritance feature:
Applied
inheritance feature:
Implementing
inheritance in C++
Syntax
:
class subclassName : access_mode baseclassName
{
... .. ...
... .. ...
};
Here, subclass_name is the name of
the sub class,
access_mode is the mode in which you
want to inherit this sub class for example: public, private etc.
base_class_name is the name of the base
class from which you want to inherit the sub class
Note: A derived class doesn’t
inherit access to private data members
Example
Program:
#include <iostream>
using namespace std;
class Parent
{
public:
int
id_p; }
// Sub class inheriting from Base
Class(Parent)
class Child : public Parent
{
public:
int
id_c; };
int main()
{
Child obj1;
obj1.id_c
= 7;
obj1.id_p
= 91;
cout
<< "Child id is " << obj1.id_c << endl;
cout
<< "Parent id is " << obj1.id_p << endl;
return
0;
}
Output:
Child
id is 7
Parent id is 91
Modes
of Inheritance (Access Specifiers)
Public
mode: If we derive a
sub class from a public base class. Then the public member of the base class
will become public in the derived class and protected members of the base class
will become protected in derived class.
Protected
mode: If we derive a
sub class from a Protected base class. Then both public member and protected
members of the base class will become protected in derived class.
Private
mode: If we derive a
sub class from a Private base class. Then both public member and protected
members of the base class will become Private in derived class.
Types
of Inheritance in C++
1. Single
Inheritance
2. Multiple
Inheritance
3. Multilevel
Inheritance
4. Hierarchical
Inheritance
5. Hybrid
(Virtual) Inheritance
Single
Inheritance
EXAMPLE
#include
<iostream>
using
namespace std;
class
Vehicle { // base class
public:
Vehicle()
{
cout << "This is a
Vehicle" << endl;
}
};
class
Car: public Vehicle{
};
int
main()
{
Car obj;
return 0;
}
Output:
This
is a vehicle
Multiple Inheritance
Multiple
Inheritance is a feature of C++ where a class can inherit from more than one
classes. i.e one sub class is inherited from more than
one base classes.
Example:
#include
<iostream>
using
namespace std;
class
Vehicle {
public:
Vehicle()
{
cout << "This is a
Vehicle" << endl;
}
};
class
FourWheeler {
public:
FourWheeler()
{
cout << "This is a 4 wheeler
Vehicle" << endl;
}
};
class Car: public Vehicle, public FourWheeler
{
};
int
main()
{
Car
obj;
return 0;
}
Output:
This
is a Vehicle
This
is a 4 wheeler Vehicle
Multilevel Inheritance
In
this type of inheritance, a derived class is created from another derived
class.
Here
class B is derived class for Class C
And
Class A is derived class for Class B. But Class A can access rights of Class B
and Class C.
Example:
#include
<iostream>
using
namespace std;
class
Vehicle
{
public:
Vehicle()
{
cout << "This is a
Vehicle" << endl;
}
};
class
fourWheeler: public Vehicle
{ public:
fourWheeler()
{
cout<<"Objects with 4 wheels
are vehicles"<<endl;
}
};
class
Car: public fourWheeler{
public:
car()
{
cout<<"Car has 4 Wheels"<<endl;
}
};
int
main()
{
Car
obj; return 0; }
output:
This
is a Vehicle
Objects
with 4 wheels are vehicles
Car
has 4 Wheels
Hierarchical Inheritance
In
this type of inheritance, more than one sub class is inherited from a single
base class. i.e. more than one derived class is created from a single base
class
Example:
#include
<iostream>
using
namespace std;
class
Vehicle
{
public:
Vehicle()
{
cout << "This is a
Vehicle" << endl;
}
};
class
Car: public Vehicle
{
};
//
second sub class
class
Bus: public Vehicle
{
};
//
main function
int
main()
{
// creating object of sub class will
// invoke the constructor of base class
Car obj1;
Bus obj2;
return 0;
}
Output:
This
is a Vehicle
This
is a Vehicle
Hybrid (Virtual) Inheritance
Hybrid Inheritance is implemented by
combining more than one type of inheritance. For example: Combining
Hierarchical inheritance and Multiple Inheritance.
Above image shows the combination of
hierarchical and multiple inheritance:
Example:
#include
<iostream>
using
namespace std;
class
Vehicle
{
public:
Vehicle()
{
cout << "This is a
Vehicle" << endl;
}
};
class
Fare
{
public:
Fare()
{
cout<<"Fare of
Vehicle\n";
}
};
class Car: public Vehicle
{ };
class
Bus: public Vehicle, public Fare
{ };
int
main()
{
Bus obj2;
return 0;
}
Output:
This
is a Vehicle
Fare
of Vehicle
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