From: Gavin Kistner <gavin@...>
Date: 2005-05-17T21:41:25+09:00
Subject: Re: Extending an Instance only Once

--Apple-Mail-1-587503984
Content-Transfer-Encoding: 7bit
Content-Type: text/plain;
	charset=US-ASCII;
	delsp=yes;
	format=flowed

On May 17, 2005, at 5:34 AM, David A. Black wrote:
> Unless I'm missing something, #is_a? would do it.

Nope, apparently it was I who missed something. Thanks :)


> The singleton class takes precedence in the sense that it comes
> earlier in the method lookup path.  (I'm assuming that you mean mixing
> the module into the class, not MyClass.extend(MyMod), which would not
> affect the class's instances.)

Indeed, that is what I meant.
   module M; end
   class Foo; end
   class Bar; include M; end
   f = Foo.new
   b = Bar.new
   f.is_a?( M )  #=> true
   b.is_a?( M )  #=> true

Yay :)



> Overall, I'm tempted to say that if you're extending a single object
> multiple times with the same module, there's something not quite right
> in the program flow.  But I doubt it's going to slow things down very
> much (but I haven't benchmarked it).

Yeah, I could certainly realize _some_ performance gain by ensuring  
that the consumer of the class ensures that they pre-mix any  
instances which are handed to the method. But I'm going for uber- 
friendliness, sort of auto-duck-typing. ("You say you don't quack  
like a duck? Here, let me strap this bill onto your head.")

When I get to benchmarking I'll check it out, but I think it should  
be fine, since this method is run only a few times during setup, and  
not during the cpu-intensive phase.

--Apple-Mail-1-587503984--