Introduction to Inheritance in C++

Inheritance is a fundamental concept in object-oriented programming (OOP) that allows a class (derived class) to inherit properties and behaviors (methods) from another class (base class). This promotes code reusability and establishes a hierarchical relationship between classes. In this article, we will discuss three practical examples of inheritance in C++, illustrating how base and derived classes work together.

Example 1: Basic Inheritance with Animals

Context

In this example, we create a base class called Animal and derived classes Dog and Cat. This demonstrates how different animals can share common properties and behaviors.

#include <iostream>
using namespace std;

// Base class
class Animal {
public:
    void eat() {
        cout << "This animal eats food." << endl;
    }
};

// Derived class 1
class Dog : public Animal {
public:
    void bark() {
        cout << "Woof! Woof!" << endl;
    }
};

// Derived class 2
class Cat : public Animal {
public:
    void meow() {
        cout << "Meow! Meow!" << endl;
    }
};

int main() {
    Dog dog;
    Cat cat;
    dog.eat();
    dog.bark();
    cat.eat();
    cat.meow();
    return 0;
}

Notes

• The Animal class contains a method eat(), which is inherited by both Dog and Cat classes.
• Each derived class has its own unique method (bark() for Dog and meow() for Cat).

Example 2: Inheritance with Constructors

Context

This example extends the previous one by adding constructors to the base and derived classes. This shows how to initialize properties for both base and derived classes.

#include <iostream>
using namespace std;

// Base class
class Animal {
protected:
    string name;
public:
    Animal(string animalName) : name(animalName) {}
    void eat() {
        cout << name << " eats food." << endl;
    }
};

// Derived class
class Dog : public Animal {
public:
    Dog(string dogName) : Animal(dogName) {}
    void bark() {
        cout << name << " says Woof!" << endl;
    }
};

int main() {
    Dog dog("Buddy");
    dog.eat();
    dog.bark();
    return 0;
}

Notes

• The Animal constructor initializes the name property.
• The Dog class constructor calls the base class constructor to set the name.

Example 3: Multi-Level Inheritance

Context

This example demonstrates multi-level inheritance by adding another derived class, Puppy, which inherits from Dog. This illustrates a more complex relationship among classes.

#include <iostream>
using namespace std;

// Base class
class Animal {
protected:
    string name;
public:
    Animal(string animalName) : name(animalName) {}
    void eat() {
        cout << name << " eats food." << endl;
    }
};

// First derived class
class Dog : public Animal {
public:
    Dog(string dogName) : Animal(dogName) {}
    void bark() {
        cout << name << " says Woof!" << endl;
    }
};

// Second derived class
class Puppy : public Dog {
public:
    Puppy(string puppyName) : Dog(puppyName) {}
    void play() {
        cout << name << " is playing." << endl;
    }
};

int main() {
    Puppy puppy("Charlie");
    puppy.eat();
    puppy.bark();
    puppy.play();
    return 0;
}

Notes

• The Puppy class inherits from the Dog class, thus gaining access to its methods.
• This example showcases the concept of multi-level inheritance, where a derived class can inherit from another derived class.