From: ara.t.howard@...
Date: 2006-07-09T15:09:52+09:00
Subject: Re: instance_exec

On Sat, 8 Jul 2006 transfire@gmail.com wrote:

> Mauricio Fernandez's looks better though --think I'll have to rip it
> for Facets ;-)

i just came across a bug in it (it's not re-entrant) - here's the fix:

   harp:~ > cat a.rb
   class Object
     unless instance_methods.include? 'instance_exec'
       def instance_exec *a, &b
         m, n = nil, -1
         loop{
           m = "__instance_exec_#{ Thread.current.object_id.abs }_#{ n += 1 }__"
           break unless respond_to? m
         }
         singleton_class{ define_method m, &b  }
         send m, *a
       ensure
         singleton_class{ undef_method m  }
       end
     end

     unless instance_methods.include? 'singleton_class'
       def singleton_class &b
         sc =
           class << self; self; end
         sc.module_eval &b if b
         sc
       end
     end
   end

   a = []

   a.instance_exec 42 do |x|
     instance_exec x do |y|
       push y
       p size
     end
   end


   harp:~ > ruby a.rb
   1


figured you'd use this if anyone would tom... cheers.


-a
-- 
suffering increases your inner strength.  also, the wishing for suffering
makes the suffering disappear.
- h.h. the 14th dali lama