From: Robert Klemme <shortcutter@...>
Date: 2006-11-19T02:20:07+09:00
Subject: Re: How to call a class method via the singleton if it exists

On 18.11.2006 18:00, Trans wrote:
> Robert Klemme wrote:
>> On 18.11.2006 16:56, Trans wrote:
>>> I want to call a class level method from the the instance level, but I
>>> need it to go through the singeton if it exists. Here is the most basic
>>> example:
>>>
>>>   class X
>>>     def self.f ; "A" ; end
>>>     def g ; self.class.f ; end
>>>   end
>>>
>>>   x = X.new
>>>   x.g  #=> "A"
>>>
>>>   def x.f; "B"; end
>>>   x.g  #=> "A"
>>>
>>> How do I get the last to return "B"? I know I could use
>>> '(class<<self;self;end)' instead of 'self.class', but that will create
>>> a singelton even if doesn't exist, which seems very wasteful. Yet I
>>> don't recall any (non-hack) way to detect if a singleton is defined. Is
>>> there?
>>>
>>> It would be nice if there was a reference with which we could call up
>>> through the class level like this.
>> Two ideas attached.
>>
>> 	robert
> 
> thanks robert. you helped clarify that unfortunately I've i mis-stated
> the problem, there's a contradiction in my example, what I actually
> meant was:
> 
>    class X
>      def self.f ; "A" ; end
>      def g ; self.class.f ; end
>    end
> 
>    x = X.new
>    x.g  #=> "A"
> 
>    # this should be:
>    class << x
>      def self.f; "B"; end
>    end
> 
>    x.g  #=> "A"  # want "B"
> 
> so #respond_to? won't help b/c I didn't intend #f to be instance level
> method. sorry. what i'm asking for, should make a whole lot more sense
> now (i hope)
> 
> thanks,
> T.


Just replace self.class with class<<self;self;end in my code.

	robert