From: ara.t.howard@...
Date: 2006-12-06T02:33:24+09:00
Subject: Re: How do I catch a missing method on a passed block?

On Tue, 5 Dec 2006, J2M wrote:

> ara.t.howard@noaa.gov wrote:
>
>> but block __will__ respond_to? 'call' - ergo your method_missing hook will
>> never fire?  what are you trying to do?
>
> I want to catch a missing method (baz) inside the passed block.

here's how to catch it:

   harp:~ > cat a.rb
   class Foo
     def bar *a, &b
       if b
         singleton_class = class << b; self; end
         singleton_class.module_eval{
           def method_missing m, *a, &b
             p [m, a, b]
           end
         }
         b.instance_eval &b
       end
     end
   end

   Foo.new.bar{ baz }

   harp:~ > ruby a.rb
   [:baz, [], nil]


and here's how to forward it to another object, in this case the Foo object:

   harp:~ > cat a.rb
   class Foo
     def bar *a, &b
       if b
         this = self
         singleton_class = class << b; self; end
         singleton_class.module_eval{
           @@this = this
           def method_missing m, *a, &b
             @@this.send m, *a, &b
           end
         }
         b.instance_eval &b
       end
     end

     def baz
       p 'baz'
     end
   end

   Foo.new.bar{ baz }


   harp:~ > ruby a.rb
   "baz"


there are many ways to skin that cat.  can you start out by just telling us
__exactly__ what you want are trying to do?  the various ways of solving this
each have consequences which could more easily be chosen from if we knew.


kind regards.


-a
-- 
if you want others to be happy, practice compassion.
if you want to be happy, practice compassion.  -- the dalai lama