Inheritance in C++

Agar aap Object-Oriented Programming (OOP) seekh rahe ho, toh Inheritance ek bahut hi powerful concept hai. Isse aap ek class ke features doosri class mein reuse kar sakte ho, bina dobara likhe.

C++ mein inheritance ka use karke hum code ko reusable, organized aur manageable bana sakte hain.

1. What is Inheritance?

Inheritance ka matlab hota hai ek class (child class) ka doosri class (parent class) se properties aur methods inherit kar lena.

Syntax:

class Derived : access_modifier Base {
    // body
};

2. Types of Inheritance in C++

a. Single Inheritance

Ek derived class sirf ek base class se inherit karti hai.

class Animal {
public:
    void eat() { cout << "Eating..." << endl; }
};

class Dog : public Animal {
public:
    void bark() { cout << "Barking..." << endl; }
};

b. Multiple Inheritance

Ek class do ya zyada base classes se inherit karti hai.

class A {
public:
    void showA() { cout << "Class A" << endl; }
};

class B {
public:
    void showB() { cout << "Class B" << endl; }
};

class C : public A, public B {
    // Inherits both A and B
};

c. Hierarchical Inheritance

Ek base class se multiple derived classes banti hain.

class Parent {
public:
    void show() { cout << "Parent class" << endl; }
};

class Child1 : public Parent {};
class Child2 : public Parent {};

d. Hybrid Inheritance

Hybrid inheritance mein multiple aur hierarchical dono ka combination hota hai. Isme ambiguity problem aa sakti hai, jise virtual inheritance se solve kiya jaata hai.

class A {
public:
    void display() { cout << "Class A" << endl; }
};

class B : virtual public A {};
class C : virtual public A {};
class D : public B, public C {};

3. Protected Access Modifier

Jab aap kisi member ko protected bana dete ho, toh:

• Base class ke andar accessible hota hai
• Derived class ke andar bhi accessible hota hai
• Lekin object ke through access nahi hota

class Base {
protected:
    int x;
};

class Derived : public Base {
public:
    void show() {
        x = 10; // Valid
        cout << "x = " << x << endl;
    }
};

4. Constructor and Destructor Calling Order

Order of Execution:

• Base class constructor → Derived class constructor
• Derived class destructor → Base class destructor

Example:

class Base {
public:
    Base() {
        cout << "Base Constructor" << endl;
    }
    ~Base() {
        cout << "Base Destructor" << endl;
    }
};

class Derived : public Base {
public:
    Derived() {
        cout << "Derived Constructor" << endl;
    }
    ~Derived() {
        cout << "Derived Destructor" << endl;
    }
};

int main() {
    Derived d;
    return 0;
}

Output:

Base Constructor  

Derived Constructor  

Derived Destructor  

Base Destructor  

Real Life Example of Inheritance

class Vehicle {
public:
    void fuel() {
        cout << "Runs on fuel" << endl;
    }
};

class Car : public Vehicle {
public:
    void wheels() {
        cout << "Has 4 wheels" << endl;
    }
};

Summary

• Inheritance lets one class acquire features of another class.
• Types: Single, Multiple, Hierarchical, Hybrid
• protected members are accessible in derived classes but not by objects.
• Constructor call order: base to derived
• Destructor call order: derived to base

Practice Questions:

• Ek Employee aur Manager class banao jisme manager Employee se inherit kare.
• Ek Shape class banao aur usse Circle, Rectangle, Triangle derive karo.