What is the difference between inheritance and polymorphism in C++?

Table of Contents

• Introduction
• Inheritance vs. Polymorphism
  • What is Inheritance?
  • What is Polymorphism?
• Key Differences
  • Purpose
  • Mechanism
  • Usage
  • Implementation
• Conclusion

Introduction

In C++, inheritance and polymorphism are two fundamental concepts of object-oriented programming (OOP) that often work together but serve different purposes. Understanding their differences and how they complement each other is crucial for designing flexible and maintainable systems.

This guide explains the distinctions between inheritance and polymorphism, illustrating how each concept functions and contributes to the object-oriented paradigm.

Inheritance vs. Polymorphism

What is Inheritance?

Inheritance is a mechanism in C++ that allows a class (known as the derived class) to inherit attributes and behaviors (methods) from another class (known as the base class). This promotes code reuse and establishes a hierarchical relationship between classes.

Key Features:

• Base Class: The class being inherited from.
• Derived Class: The class that inherits from the base class.
• Access Specifiers: Public, protected, and private inheritance define the visibility of base class members in the derived class.

Example of Inheritance:

Output:

What is Polymorphism?

Polymorphism allows objects of different classes to be treated as objects of a common base class, particularly when using pointers or references. This capability enables methods to operate on objects of different types through a common interface, which enhances flexibility and code reuse.

Types of Polymorphism:

1. Compile-Time Polymorphism (Static Polymorphism): Achieved through function overloading and operator overloading.
2. Run-Time Polymorphism (Dynamic Polymorphism): Achieved through inheritance and virtual functions, allowing the method called to be determined at runtime.

Example of Polymorphism:

Output:

Key Differences

Purpose

• Inheritance: Provides a mechanism for creating new classes based on existing ones, promoting code reuse and establishing class hierarchies.
• Polymorphism: Enables objects of different classes to be treated uniformly through a common base class interface, allowing methods to operate on objects of varying types dynamically.

Mechanism

• Inheritance: Achieved through deriving new classes from existing ones, inheriting their attributes and methods.
• Polymorphism: Achieved using virtual functions in conjunction with base class pointers or references to allow dynamic method binding.

Usage

• Inheritance: Used to express "is-a" relationships between classes. For instance, a Dog "is-a" type of Animal.
• Polymorphism: Used to express "can-do" relationships, allowing different objects to be processed through a common interface. For instance, both Dog and Cat can "makeSound" in their own way.

Implementation

• Inheritance: Implemented using class declarations and access specifiers. Derived classes inherit and may extend or override base class functionality.
• Polymorphism: Implemented using virtual functions and pointers or references to base classes. It requires dynamic dispatch to determine the appropriate method implementation at runtime.

Conclusion

Inheritance and polymorphism are integral to C++'s object-oriented approach, each serving distinct roles in code design. Inheritance allows the creation of new classes from existing ones, promoting reuse and hierarchical relationships. Polymorphism enables the treatment of objects of different types through a common interface, facilitating flexibility and extensibility in method operations. Mastery of both concepts is essential for designing robust and adaptable C++ programs.