From: Greg Hurrell <greg.hurrell@...>
Date: 2007-01-24T18:50:10+09:00
Subject: Can Ruby do the Objective-C/Cocoa style alloc/init pattern?

In Objective-C/Cocoa objects normally come to life in the following
way:

instance = [[Class alloc] init];

The "Class" is sent an "alloc" message (memory is allocated and a new
instance is actually created) and then the new instance is sent an
"init" message (allowing the object to prepare itself for use).

This pattern allows you do some cool dynamic things. For example, in
your "init" method you can actually return a different object than the
one that was allocated. This is pretty cool because it means you can
return objects of different classes depending on the parameters that
are passed to your "init" method.

Is there any way to do something similar in Ruby? Sending "new" to a
class in Ruby is kind of like doing an "alloc" in Objective-C/Cocoa,
and the Ruby "initialize" method is similar to the Objective-C/Cocoa
"init" method; but unlike Objective-C/Cocoa it really doesn't matter
what you return from your "initialize" method so there doesn't seem to
be any way to return an object of a different class.

I can think of ways to fake this pattern but I am not sure if they're
the best idea. For example, I could add a new class method (could even
call it "alloc" if I wanted) and a new instance method "init" and
basically fake the Cocoa/Objective-C behaviour; but I don't want to
deform Ruby until it looks like Objective-C, I'd rather find a means of
implementing this pattern the "Ruby Way".

What do the experienced Rubyists have to say?

Cheers,
Greg