From: Lionel Thiry <lthiryidontwantspam@...>
Date: 2005-04-30T05:54:43+09:00
Subject: Re: determining when inside 'class << self'

Mark Hubbart a �crit :
> On 4/29/05, Florian Gro� <florgro@gmail.com> wrote:
> 
>>Lionel Thiry wrote:
>>
>>
>>>>  class << []
>>>>    p inside_metaclass? #=> true
>>>>  end
>>>
>>>Sorry for the newbie question, but what does this mean?
>>
>>class << obj enters the idioclass of an object which is a class that
>>contains method that will only be defined for that particular object.
> 
> 
> Florian: Great explanation.

Yeah, great. :)

But I already knew about the singleton methods and their container object, the 
said idioclass. But I didn't know well all the subtleties of 'class << obj', 
hence my initial question.

> 
> Lionel: If 'class << []' itself seems a little odd to you, read on...
> 

Ok, I read, I read! :)

> The class << obj notation can be used in ways that you might not
> expect. Since ruby syntax is not as ridged as some other languages,
> any expression can take the place of 'obj' in that notation. For
> example, if you want to create a temporary/mock object of some sort:
> 
> def clear
>   class << (a = Object.new)
>     def inspect() `clear` end
>   end
> end
> 
> (this example was pulled right out of my irbrc)
> 
> As you can see, 'a' was assigned to, and then the resulting object was
> opened for modification. So this code:
> 
> class << []
>   # do stuff
> end
> 
> .. just creates an anonymous array and opens it's metaclass (or
> idioclass or singleton class or virtual class, whatever). However, the
> array is never assigned to a variable, so it will probably be garbage
> collected pretty soon. You will probably never see this exact thing in
> someone's code, but it is possible.

This probably explains why it was so odd to me, I've mainly met the 'class << 
self' version.

Thanks a lot to you all! :)

-- 
Lionel Thiry

Personal website: http://users.skynet.be/lthiry/