From: "David A. Black" <dblack@...>
Date: 2008-03-22T01:32:04+09:00
Subject: Re: dynamically defining a method on an instance that references vars in  enclosing scope?

Hi --

On Sat, 22 Mar 2008, Christopher J. Bottaro wrote:

> Hello.  I want to do this.
>
> instance = MyClass.new
> x = 1
> def instance.foo
>  puts x
> end
> undefined local variable or method `x' for #<MyClass:0x31ca8c4>
>
> How do get rid of that error?

You can use define_method, which takes a block and therefore can use
the local variables in scope at the time it's called. You'd have to do
something equivalent to the familiar:

   class Object
     def singleton_class
       class << self
         self
       end
     end
   end

(Aside to Matz: can we *please* have that in 1.9/2.0? :-)

and then:

   instance.singleton_class.class_eval {
     define_method("foo") { puts x }
   }


David

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