From: "David A. Black" <dblack@...>
Date: 2005-04-04T11:30:52+09:00
Subject: Re: signleton_methods / methods / public_methods - weirdness?

Hi --

On Mon, 4 Apr 2005, Saynatkari wrote:

> David A. Black wrote:
>> 
>>   irb(main):001:0> class A; def A.x; end; end; class B < A; end
>>   => nil
>>   irb(main):002:0> B.singleton_methods(false)
>>   => []
>>   irb(main):003:0> B.singleton_methods(true)
>>   => ["x"]
>> 
>> I would argue that there is a bit of a contradiction here, arising
>> from the special case of inheritance.  x is not really a singleton
>> method of B; it's a singleton method of B's superclass, and the rules
>> of inheritance allow the (arguably anomalous) behavior that the
>> subclass can serve as the receiver for what would otherwise be a truly
>> singleton method.
>> 
>> I believe this is the only scenario where, after doing this:
>> 
>>   def obj.meth; end
>> 
>> any object other than obj can call meth.  In other words, a Class's
>> singleton methods ("class methods") don't quite behave in a singleton
>> fashion.
>
> other = obj.clone

But in that case, the clone is calling its own singleton method of the
same name:

   irb(main):001:0> a = Object.new
   => #<Object:0x4029aa34>
   irb(main):002:0> def a.x; 1; end
   => nil
   irb(main):003:0> b = a.clone
   => #<Object:0x40295b4c>
   irb(main):004:0> b.x
   => 1
   irb(main):005:0> def a.x; 2; end
   => nil
   irb(main):006:0> b.x
   => 1

(I'm actually not sure whether the 'x' prior to the redefinition of
a#x is the same for both objects.  If so, it's just an optimization,
since b#x is a different method after a#x is redefined.)


David

-- 
David A. Black
dblack@wobblini.net