In c++, are the virtual function, function overriding and polymorphism related with each other?

Question

Generally in C++, we see same name functions with same arguments in different classes along with virtual keyword. Is it an example of polymorphism? If it is, how and is there any other way to understand polymorphism in c++??

Are you specifically referring to subtype polymorphism? Overloading and templates are two other examples of polymorphism in C++. — , May 04 '14 at 20:31
Maybe this [link](http://www.cplusplus.com/doc/tutorial/polymorphism/) can help you — Salvatore Avanzo, May 04 '14 at 20:43
@rightfold: no, not any specific type of polymorphism. I just want to know what is relation of function override or virtual function with polymorohism? And as you give two more, how can we call overloading and template example of polymorphism? — Omor Faruk Mashuk, May 04 '14 at 20:47

score 1 · Accepted Answer · edited May 23 '17 at 12:28

Suppose that you have the following scheme:

class Base {
  public:
    virtual int foo() = 0;
};

class Derived1 : public Base {
  public:
    virtual int foo() { return 1; }
};

class Derived2 : public Base {
  public:
    virtual int foo() { return 2; }
};

Lets say now, that you want to store objects of Derived1 and Derived2 in a container, lets say a std::vector and every time you iterate through the vector to call for each one of its objects function foo. Normally, you'd need two vectors, one for objects of class Derived1 and another one for objects of class Derived2.

Look now how polymorphism comes to our rescue. We can store the addresses of objects Derived1 and Derived2 as pointers to Base objects, and then store these pointers in a std::vector<Base*> v. Now every time we iterate the vector of pointers and call member function foo (e.g., for(auto base : v) base->foo()) the right function foo is called for each one of the objects. This is one of the many aspects of polymorphism which is called upcasting

I hope that the above example of runtime polymorphism gave you a clue, as for how virtual functions and function overriding are related to inheritance and polymorphism.

Update:

Templates are a form of compile time polymorphism take a look at this SO question what is the difference between templates and polymorphism.

In c++, are the virtual function, function overriding and polymorphism related with each other?

1 Answers1