Polymorphism is an important concept in object-oriented programming. It seems to mean different things to different people. Try Googling it and you will see what I mean. I think that these are two of the best definitions that I have found.



I found that one in an article about polymorphism in C++.

This is the second:



That one is from wikipedia.

This all stemmed from a topic in the C# http://www.dreamincode.net/forums/showtopic102750.htm

i dont see a problem ? they both describe it.

I was not saying there was a problem with them.

It just seemed to me that the first seems to lead toward the idea that polymorphism is all about overloading methods and operators inside a class because of the rest of the article.

The second seems to lead toward the idea that polymorphism is more about inheritance and virtual methods that will be changed when the object is inherited.

It is just can be a hard concept for somebody new to OOP might find difficult to understand and I was more trying to start a discussion on what polymorphism meant to others on this site so it would be easy for those new to OPP to understand.

I think I've found a bit better article that explains what polymorphism is to a programmer. (Though it was specifically from the C# programming guide on MSDN.)



In an RPG polymorph is used to describe changing form from say a person into a dragon.

Damn it. I totally didn't see this thread before I made mine

I forget to come to this forum on occasion. There's a similar thread in the C++ discussion area.

This post has been edited by KYA: 2 May, 2009 - 06:33 PM

I think it deserves a close look in both, it can be a tricky concept for people new to programming to understand and I don't think very many read this forum.

I will talk in terms of C++. Polymorphism is the hability to call to the functions of a derived object using a pointer of the base class type.

A good example is the ability to pass in an inherited instance of an object to a method that accepts a parameter of the base classes type.

public void GetX(baseType bt){};

You could use this method as:

GetX(inheritedObjectInstance);

And this is valid because of dynamic binding.

Please correct me if I'm wrong, it's been a long time since working with this.

if there are 3 classes --BASE,derived1,derived2 and base contains a pure virtual function

then
Polymorphism simply means --

we can use the same function in different ways by just exchanging the addresses in the base class pointer..(exchanging with derived1 and derived2)

Right, polymorphism and inheritance are often intertwined. Polymorphism is attained through inheritance. It is of course possible to have inheritance without polymorphism, though.

Nice distinction LoveIsNull, It may be best, (as in most helpful to understanding Polymorphism) to talk about it in the terms of what benefits polymorphism achieves.



What advantage does this give us? Well, most descriptions I have seen use it to provide a generic interface for a virtual class (in C++) This just means that it's a set of methods that can be called no matter what instance your working with... Lets say we have an Animal class, and from this class we inherit the Snake class and the Horse class. The generic interface might have a method called move() that is implemented differently in each of the inherited classes.. one causing the snake to slither along and the other causing the horse to gallop or trot..

One of the benefits of this type of implementation is that if you add another class, say..Bird there are no changes that need to be made to the interface.. the move function can still be called but the implementation will be different for an instance of the Bird class..flying obviously.

This is a benefit of polymorphism, and by describing the benefits of it.. hopefully what it is becomes a little more clear to people that are not familiar with it.

Aet

poly means many

morphism means forms

polymorphism == many forms

above understanding given by snowflakes is the simplest one...

also, i would say that polymorphism is of two types:
compile-time:fuction overloading,operator overloading
run-time:virtual functions
you can get many tutorials and snippets if you want to see how these are implemented

so actually polymorphism is a bit of everything that has been written in various posts of this forum