Understanding Inheritance and Polymorphism in C++

1. Introduction

Welcome to this tutorial on understanding inheritance and polymorphism in C++. Our goal is to give you a solid understanding of these two fundamental concepts in object-oriented programming.

You will learn:

• The concept of inheritance
• The concept of polymorphism
• How to implement inheritance and polymorphism in C++

Prerequisites:

• Basic understanding of C++ programming language
• Familiarity with object-oriented programming concepts

2. Step-by-Step Guide

Inheritance

Inheritance is a feature of object-oriented programming that allows a class (child or derived class) to inherit properties and methods from another class (parent or base class). It promotes code reusability and hierarchy of classes.

Let's consider an example:

class Animal {                  // Parent class
  public:
    void eat() {
      cout << "I can eat!" << endl;
    }
};

class Dog : public Animal {     // Child class
  public:
    void bark() {
      cout << "I can bark!" << endl;
    }
};

In the above code, Dog is a derived class that inherits from the Animal base class. Therefore, an object of the Dog class can access the eat() method.

Polymorphism

Polymorphism is another feature of object-oriented programming that allows one function to behave differently based on the object that calls it. It provides flexibility while designing large functional units.

Here's an example:

class Animal {
  public:
    virtual void sound() {
      cout << "Animals can make sound!" << endl;
    }
};

class Dog : public Animal {
  public:
    void sound() override {
      cout << "Dog barks!" << endl;
    }
};

In the above code, sound() in the Dog class overrides the sound() in the Animal class. This is an example of polymorphism.

3. Code Examples

Let's look at some more practical examples:

Inheritance

class Animal {                  // Base class
  public:
    void eat() {
      cout << "I can eat!" << endl;
    }
};

class Dog : public Animal {     // Derived class
  public:
    void bark() {
      cout << "I can bark!" << endl;
    }
};

int main() {
  Dog dog1;
  dog1.eat();                   // Accessing method of parent class
  dog1.bark();                  // Accessing method of child class
  return 0;
}

Expected output:

I can eat!
I can bark!

Polymorphism

class Animal {
  public:
    virtual void sound() {          // Virtual function
      cout << "Animals can make sound!" << endl;
    }
};

class Dog : public Animal {
  public:
    void sound() override {         // Overriding function
      cout << "Dog barks!" << endl;
    }
};

int main() {
  Animal* baseptr;                  // Base class pointer
  Dog dog1;
  baseptr = &dog1;

  baseptr->sound();                 // Late binding occurs
  return 0;
}

Expected output:

Dog barks!

4. Summary

We have covered the following topics:

• Inheritance and how it promotes code reusability
• Polymorphism and how it provides flexibility in designing large functional units
• Implementing inheritance and polymorphism in C++

Next steps for learning:

• Dive deeper into different types of inheritance - single, multiple, multilevel, hierarchical, and hybrid inheritance.
• Learn about different types of polymorphism - compile-time and runtime polymorphism.

5. Practice Exercises

1. Create a base class Vehicle and derived classes Car and Bike with some properties and methods.

2. Implement polymorphism with a base class Shape and derived classes Circle and Rectangle. Each class should have a method area() that calculates and prints the area.

Solutions and explanations will be provided upon request.

These exercises will help you gain a practical understanding of inheritance and polymorphism in C++. Continue practicing to solidify the concepts.