Polyphorism

FastFullBack

Ok so I've got an interview for a graduate development job tomorrow and no matter how books I read I can't get a good definition for good ole polyphorism.

I've got an understanding of this in my head but trying to put that into words that an interviewer might understand is where I always fumble.

Anyone got any good 5 or 6 line description.

Any response before half 5 would be great.

Regards,
Tim

Enygma

Maybe cause your searching for the wrong thing, try polyMORphism.

Incidentally, when I was learning Java it was a Spanish guy teaching us, he came in at the start of the lesson and wrote it up on the board, every time he needed to say "polymorphism" he'd say "that word on the board"

misterfoo

Well, having an understanding in your head is better than having a definition to parrot. If the interviewer wants a literal definition rather than a demonstration that you understand the concept, then the only right answer is the one from the OO programming book the interviewer has on their shelf. You can demonstrate an understanding by citing examples and sketching out what they have in common. You can especially demonstrate an understanding if you can point out a use of polymorphism in material that the interviewer has brought up and that you've never seen before.

Polymorphism is something like:
standard global messages + custom local message handling
or
standard public method signatures (in abstract classes & interfaces) + custom local method implementations (in subclasses)
Polymorphism is good in less than 25 words because: standard global messages => loose coupling, stable architecture, reuse of infrastructure, etc; custom local message handling => flexibility, customisability, modifiability, etc.

An example of polymorphism: if you click on Open or Print in the rightclick menu of a file in Windows, you're sending a standard message that's responded to in different ways by the different types of file.

(I think that's polymorphism anyway, unless I'm mixing it up with some other Good Thing).

padlad

"Polymorphism (means the ability to take more than one form) is the ability of different functions to be invoked with the same name.

There are two forms.
Static polymorphism is the common case of overriding a function by providing additional definitions with different numbers or types of parameters. The compiler matches the parameter list to the appropriate function.

Dynamic polymorphism is different and relies on parent classes to define virtual functions which child classes may redefine. When this virtual member function is called for an object of the parent class, the execution dynamically chooses the appropriate function to call - the parent function if the object really is the parent type, or the child function if the object really is the child type. "

clear?

The Corinthian

carrolltimmy wrote:

Anyone got any good 5 or 6 line description.

Any response before half 5 would be great.

Would you like one of us to sit the interview for you? Maybe make you breakfast too..?

Talliesin

I've only ever seen static polymorphism defined as the use of templates to determine functionality at compile time, not over-loading.

The term on its own tends to mean dynamic polymorphism.

misterfoo

I've never found the word itself much use. Nobody says "we need to throw in a little polymorphism over there", they say "can we get rid of that dependency", or they say "can we modify that behaviour in the subclass". I've never found it very useful to think of it as the ability to take on many forms - that just reminds me of Superman.

'Polyphorism' probably means the ability to carry many things.

madramor

you should be able to give a real world description of polymorphism
if you have vehicles
car and boat and jet
to move vehicle you go vehicle.move()
car.move() turn the wheels
boat.move() rotate the propeller
jet.move() blow air out jets

and also a coded example, best if, from where you have used it.
best examlpe is the action classes from MVC architecture
http://java.sun.com/blueprints/guidelines/designing_enterprise_applications_2e/web-tier/web-tier5.html#1080752
section 4.4.2.1.2 Invoking Model Methods

carrolltimmy wrote:

I've got an understanding of this in my head but trying to put that into words that an interviewer might understand is where I always fumble.

if you cannot communicate it to another person, it means you don't
understand it properly.

ps i'm interviewing grads this week for junior developer roles