Polymorphism

Polymorphism

Polymorphism meaning having many forms.

In C++ there are two types of polymorphism

• Compile-time polymorphism
• Run-Time polymorphism

Compile time polymorphism 

The binding happens at compile time, meaning based on the arguments the compiler tries to interpret the function call.

It can be observed with function overloading. Based on the type of arguments passed, the compiler decides which function to call. 

	int add(int a, int b) {
	return a + b;
	}
	int add(int a, int b, int c) {
	return a + b + c;
	}
	void main()
	{
	/*depending on the number of the arguments passed
	compiler decides which method to call
	*/
	add(1,2);
	add(1,2,3);
	}

view raw polymorphism.cpp hosted with ❤ by GitHub

Run time polymorphism 

The binding happens at run time. Function over-riding is an example of Run-time polymorphism.
Here is a simple example of Run-time polymorphism.

	class Animal {
	public:
	//remove the virtual keyword here to avoid dynamic binding
	virtual void sound() {
	}
	};
	class Cat :public Animal {
	void sound() {
	cout << "Meow" << endl;
	}
	};
	class Dog :public Animal {
	void sound() {
	cout << "Woof" << endl;
	}
	};
	void makesound(Animal*ptr)
	{
	ptr->sound();
	}
	int main()
	{
	Animal*catptr = new Cat();
	Animal*dogptr = new Dog();
	makesound(catptr);
	makesound(dogptr);
	return 0;
	}

view raw RT_polymorphism.cpp hosted with ❤ by GitHub

In the above example, based on the type of the object the pointer is holding we would want the function to be called. If it is Dog pointer, then the Dog class's sound method is executed. This feature of the compiler to identify the type of object at run time and call the correct method is called Run time polymorphism. For this to occur the base class should have atleast one virtual function.