Re: What is polymorphism?

=?ISO-8859-1?Q?Erik_Wikstr=F6m?= <>
Tue, 06 Jun 2006 18:00:31 GMT
On 2006-06-06 19:39, Seigfried wrote:

"I could train my dog to respond to the command 'bark' and my bird to
respond to the command 'chirp.' On the other hand, I could train them
to both respond to the command "speak." Through polymorphism, I know
that the dog will respond with a bark and the bird will respond with a

Not quite C++ syntax, but we're dealing with concepts here.

Just a few paragraphs further on, the same book states:

"In OOP, you implement this type of polymorphism through a process
called overloading. You can implement different methods of an object
that have the same name."


Yeah ... but "bird and "dog" are DIFFERENT names. Of course you can
call different objects and get different results. I thought the key
concept behind "polymophism" was "same name - different SIGNATURE -
different methods" - not "different names". This was the crux of my

Try to think of it like this, there is a class called Animal which has a
method called speak(). Dog and Bird are both derived from Animal and
thus both have the method speak(), but they overload this method with a
version appropriate for whatever kind of animal they are.

Thus when the command speak is given it is not given to the dog, it is
given to an animal, and that animal then uses it's own implementation of
speak. This is the "same name"-thing you are talking about. You don't
need to know if it's a dog or a bird, just that it's an animal and that
an animal can perform certain tasks.

Erik WikstrFm
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