Dynamic Dispatch

Explanation:

• Dynamic dispatch means deciding which method to call at runtime based on the object type, not reference type.

• Achieved using virtual functions in C++ and method overriding in Java.

• Implemented internally using a V-Table (Virtual Table).

  • Each class with virtual methods has a table storing function pointers.

  • Each object has a hidden pointer (vptr) to its class’s V-Table.

  • At runtime, vptr is checked to call the correct function.

CopyCopy#include <iostream>
using namespace std;

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

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

int main() {
    Animal* a = new Dog();
    a->speak();  // "Dog barks" -> runtime decision (dynamic dispatch)
}

• Base* ptr = new Derived(); → Classic polymorphism.

• Why not Drawable d = new Circle();? → Abstract class cannot be instantiated, object slicing.

• Why not Circle* d = new Circle();? → Works, but loses polymorphism.

• Why not Circle d = new Circle();? → Wrong, because new gives pointer, not object.