Ruby OO (Re: About top-level method)

Sam Sungshik Kong wrote:
> I'm getting more and more confused...
> Before I started Ruby, I thought I understood OOP concepts very clearly
> (with Java, C#, even Python).
> But Ruby puts me in a deep confusion with singleton methods, somewhat
> different concept of private/protected accessibility, metaclass, etc...


Java and (to the best of my knowledge) C# have a particular philosophy 
of OO that differs from Ruby (and probably Python).

My understanding of OO tends to center on the notion of sending messages 
to receivers; the receiver may or may not know how to handle the 
message.  The receiver may have originated from  a class derived from 
one or more other classes, but, once created, may have acquire new or 
altered behavior not found in any of the base class(es).  Messages sent, 
and methods implemented in the receiver, should not have to map to one 
another; how an object responds to a message is up to that particular 
object.  The default behavior for handling unknown messages tends to be 
an exception, but that should be left to the object (i.e., the 
developer), not hard-coded into the language.

By analogy, think of a web site.  Pages generally map to specific URLs. 
  Many web sites simply toss back a 500 or 404 when given an unknown 
request, but the smarter sites know how to map all URLs to something 
useful.  Now imagine if a web site was operationally prevented from 
handling unknown URLs.  Or if a user could not even *try* to request a 
page without knowing the full, correct URL in advance.  (The 
statically-typed Web?)

This view of OO runs counter to statically typed languages such as Java 
and C#, where behavior tends to be set in stone early on, and object 
behavior is defined by method invocation rather than message handling.

The idea that one object may be able to respond to messages that another 
object of the same class cannot is alien in Java, but normal in Ruby.

Likewise, the idea that classes and objects are malleable during runtime 
is largely foreign in Java, but an essential fact of Ruby.

I'm not sure how much any of this helps you with your actual problem :); 
I'm not even sure how accurate it is*.   Getting your head around Ruby 
is may be an adventure if you're coming from Java/C#.

There's also a good take on what constitutes various flavors of OO on 
Paul Graham's site [0].  (There's lot's of other good stuff on his site, 
BTW.  I particularly like his comments on Arc and OO [1])



James

* I'm trusting somebody here will promptly correct me where I'm wrong. 
But no flamewars, please.

[0] http://www.paulgraham.com/reesoo.html
[1] http://www.paulgraham.com/noop.html