From: Massimiliano Mirra <list@...>
Date: 2002-07-09T22:41:24+09:00
Subject: Re: self_parent

On Tue, Jul 09, 2002 at 03:51:24PM +0900, Tom Sawyer wrote:
> class A
>   def initialize(x)
>     x.call
>   end
>   def display
>     puts 'hello'
>   end
> end
> 
> class B
>   def initialize(x)
>     x.call
>   end
>   def display
>     puts 'goodbye'
>   end
> end
> 
> x = OpenProc { display }
> 
> A.new(x) --> hello
> B.new(x) --> goodbye
> 
> in this way an object can, in effect, ask another object what it should
> do. and that is what i was accomplishing, albiet in a lame way, by
> passing self (and wanting self_parent for).
> 
> so, is there any way to readily accomplish this in ruby?

One way could be to use eval with a binding coming from the object,
e.g.:

class A
  def get_binding
    return binding
  end

  def display
    puts 'hello'
  end
end

a = A.new
eval("display", a.get_binding)

But eval is evil. :-)


Another is what I think is called a `singleton method':

a = A.new
def a.do_this
  display
end
a.do_this


However, it would be nice if Proc objects could refer not necessarily
to the context where they were created, but to an arbitrary one.  But
I suspect this would pose many difficulties.

Massimiliano