Inheritance
Inheritance
March 09, 2021
C++ Inheritance
In C++, inheritance is a process in which one object acquires all the properties and behaviors of its parent object automatically. In such way, you can reuse, extend or modify the attributes and behaviors which are defined in other class.
In C++, the class which inherits the members of another class is called derived class and the class whose members are inherited is called base class. The derived class is the specialized class for the base class.
Advantage of C++ Inheritance
Code reusability: Now you can reuse the members of your parent class. So, there is no need to define the member again. So less code is required in the class.
Types Of Inheritance
C++ supports five types of inheritance:
Single inheritance
Multiple inheritance
Hierarchical inheritance
Multilevel inheritance
Hybrid inheritance
C++ Inheritance Derived Classes
A Derived class is defined as the class derived from the base class.
The Syntax of Derived class:
class derived_class_name :: visibility-mode base_class_name
{
// body of the derived class.
}
Where,
derived_class_name: It is the name of the derived class.
visibility mode: The visibility mode specifies whether the features of the base class are publicly inherited or privately inherited. It can be public or private.
base_class_name: It is the name of the base class.
When the base class is privately inherited by the derived class, public members of the base class becomes the private members of the derived class. Therefore, the public members of the base class are not accessible by the objects of the derived class only by the member functions of the derived class.
When the base class is publicly inherited by the derived class, public members of the base class also become the public members of the derived class. Therefore, the public members of the base class are accessible by the objects of the derived class as well as by the member functions of the base class.
Note:
In C++, the default mode of visibility is private.
The private members of the base class are never inherited.
C++ Single Inheritance
Single inheritance is defined as the inheritance in which a derived class is inherited from the only one base class.
Where 'A' is the base class, and 'B' is the derived class.
C++ Single Level Inheritance Example: Inheriting Fields
When one class inherits another class, it is known as single level inheritance. Let's see the example of single level inheritance which inherits the fields only.
#include <iostream>
using namespace std;
class Account {
public:
float salary = 60000;
};
class Programmer: public Account {
public:
float bonus = 5000;
};
int main(void) {
Programmer p1;
cout<<"Salary: "<<p1.salary<<endl;
cout<<"Bonus: "<<p1.bonus<<endl;
return 0;
}
Output:
Salary: 60000
Bonus: 5000
In the above example, Employee is the base class and Programmer is the derived class.
C++ Multilevel Inheritance
Multilevel inheritance is a process of deriving a class from another derived class.
C++ Multi Level Inheritance Example
When one class inherits another class which is further inherited by another class, it is known as multi level inheritance in C++. Inheritance is transitive so the last derived class acquires all the members of all its base classes.
Let's see the example of multi level inheritance in C++.
#include <iostream>
using namespace std;
class Animal {
public:
void eat() {
cout<<"Eating..."<<endl;
}
};
class Dog: public Animal
{
public:
void bark(){
cout<<"Barking..."<<endl;
}
};
class BabyDog: public Dog
{
public:
void weep() {
cout<<"Weeping...";
}
};
int main(void) {
BabyDog d1;
d1.eat();
d1.bark();
d1.weep();
return 0;
}
Output:
Eating...
Barking...
Weeping...
C++ Multiple Inheritance
Multiple inheritance is the process of deriving a new class that inherits the attributes from two or more classes.
Syntax of the Derived class:
class D : visibility B-1, visibility B-2, ?
{
// Body of the class;
}
Let's see a simple example of multiple inheritance.
#include <iostream>
using namespace std;
class A
{
protected:
int a;
public:
void get_a(int n)
{
a = n;
}
};
class B
{
protected:
int b;
public:
void get_b(int n)
{
b = n;
}
};
class C : public A,public B
{
public:
void display()
{
std::cout << "The value of a is : " <<a<< std::endl;
std::cout << "The value of b is : " <<b<< std::endl;
cout<<"Addition of a and b is : "<<a+b;
}
};
int main()
{
C c;
c.get_a(10);
c.get_b(20);
c.display();
return 0;
}
Output:
The value of a is : 10
The value of b is : 20
Addition of a and b is : 30
In the above example, class 'C' inherits two base classes 'A' and 'B' in a public mode.
C++ Hybrid Inheritance
Hybrid inheritance is a combination of more than one type of inheritance.
Let's see a simple example:
#include <iostream>
using namespace std;
class A
{
protected:
int a;
public:
void get_a()
{
std::cout << "Enter the value of 'a' : " << std::endl;
cin>>a;
}
};
class B : public A
{
protected:
int b;
public:
void get_b()
{
std::cout << "Enter the value of 'b' : " << std::endl;
cin>>b;
}
};
class C
{
protected:
int c;
public:
void get_c()
{
std::cout << "Enter the value of c is : " << std::endl;
cin>>c;
}
};
class D : public B, public C
{
protected:
int d;
public:
void mul()
{
get_a();
get_b();
get_c();
std::cout << "Multiplication of a,b,c is : " <<a*b*c<< std::endl;
}
};
int main()
{
D d;
d.mul();
return 0;
}
Output:
Enter the value of 'a' :
10
Enter the value of 'b' :
20
Enter the value of c is :
30
Multiplication of a,b,c is : 6000
C++ Hierarchical Inheritance
Hierarchical inheritance is defined as the process of deriving more than one class from a base class.
Syntax of Hierarchical inheritance:
class A
{
// body of the class A.
}
class B : public A
{
// body of class B.
}
class C : public A
{
// body of class C.
}
class D : public A
{
// body of class D.
}
Let's see a simple example:
#include <iostream>
using namespace std;
class Shape // Declaration of base class.
{
public:
int a;
int b;
void get_data(int n,int m)
{
a= n;
b = m;
}
};
class Rectangle : public Shape // inheriting Shape class
{
public:
int rect_area()
{
int result = a*b;
return result;
}
};
class Triangle : public Shape // inheriting Shape class
{
public:
int triangle_area()
{
float result = 0.5*a*b;
return result;
}
};
int main()
{
Rectangle r;
Triangle t;
int length,breadth,base,height;
std::cout << "Enter the length and breadth of a rectangle: " << std::endl;
cin>>length>>breadth;
r.get_data(length,breadth);
int m = r.rect_area();
std::cout << "Area of the rectangle is : " <<m<< std::endl;
std::cout << "Enter the base and height of the triangle: " << std::endl;
cin>>base>>height;
t.get_data(base,height);
float n = t.triangle_area();
std::cout <<"Area of the triangle is : " << n<<std::endl;
return 0;
}
Output:
Enter the length and breadth of a rectangle:
23
20
Area of the rectangle is : 460
Enter the base and height of the triangle:
2
5
Area of the triangle is : 5
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