C++ Virtual Functions

🎭 C++ Virtual Functions – One Name, Many Forms at Runtime

In C++, a virtual function lets you create a function in a base class and override it in a derived class — then call the correct version at runtime using a base class pointer. It’s a smart way to get polymorphism working! 🧠

🔍 What is a Virtual Function?

A virtual function is a member function in a base class that you expect to be redefined in derived classes. It’s marked with the keyword virtual. At runtime, C++ figures out which function to run based on the actual object type — not just the pointer type.

💡 Syntax

class Base {
public:
    virtual void speak() {
        // base version
    }
};

🔧 Example: Using Virtual Function

#include <iostream>
using namespace std;

class Animal {
public:
    virtual void speak() {
        cout << "Animal speaks" << endl;
    }
};

class Cat : public Animal {
public:
    void speak() override {
        cout << "Cat meows" << endl;
    }
};

int main() {
    Animal* pet;
    Cat kitty;

    pet = &kitty;
    pet->speak(); // Calls Cat's version at runtime

    return 0;
}
  

📌 Key Points

• Declared using the virtual keyword in the base class
• Used to achieve runtime polymorphism
• Enables dynamic method resolution
• Usually overridden using override keyword in derived class

⚠️ Virtual vs Non-Virtual

• Virtual: Resolved at runtime (dynamic binding)
• Non-virtual: Resolved at compile time (static binding)

🧠 Why Use Virtual Functions?

• Allows different behavior for the same function name
• Makes code more flexible and extensible
• Used heavily in real-world object-oriented systems

🧾 Summary

• Use virtual in the base class when expecting overriding
• Pointer to base class calls correct derived method at runtime
• This is the heart of runtime polymorphism
• One name, many forms — that’s virtual magic! ✨