From: Pit Capitain <pit@...>
Date: 2007-03-07T19:56:35+09:00
Subject: Re: object_* and instance_* methods

Brian Candler schrieb:
> On Wed, Mar 07, 2007 at 06:40:20PM +0900, Brian Candler wrote:
>> Final point. If the requirement is that 'meta-programming' methods should be
>> available always on all objects, then I can offer a completely different
>> solution:
>>
>>     # was: foo.class
>>     Object.class_of(foo)
>>
>>     # was: foo.send(meth,*args)
>>     Object.send_to(foo, meth, *args)
>>
>>     # was: foo.method(:bar)
>>     Object.method_of(foo, :bar)
>>
>> That is, by making all these operations singleton methods of a module,
>> instead of (or as well as) instance methods which are present on all
>> objects, then there is never any chance of them being overriden by the
>> object itself. It's not very OO-like, but it *is* immune from this problem.
> 
> And this is straightforward to implement:
> 
> ----- 8< -------------------------------------------------------
> module Meta
>   def self.send(obj, meth, *args)
>     Object.instance_method(:send).bind(obj).call(meth, *args)
>   end
> 
>   def self.class(obj)
>     Object.instance_method(:class).bind(obj).call
>   end
> 
>   # etc
> end
> 
> class Foo
>   def send(*args)
>     "whoo!"
>   end
>   def class
>     "stupid!"
>   end
> end
> 
> f = Foo.new
> 
> puts f.class                     # stupid!
> puts Meta.class(f).inspect       # Foo
> 
> puts f.send(:object_id)          # whoo!
> puts Meta.send(f, :object_id)    # -605608944
> ----- 8< -------------------------------------------------------
> 
> Implement all the methods you consider to be "metaprogramming" with whatever
> names you think are appropriate. Stick it up as a module on rubyforge, in
> case anyone comes across the same need as you. Job done, and no need to
> change the core language :-)

Brian, this looks a lot like the concept of "mirrors" in the language 
Self. See for example http://bracha.org/mirrors.pdf for a discussion. I 
like this approach.

Regards,
Pit