From: Pit Capitain <pit.capitain@...>
Date: 2008-10-08T02:57:45+09:00
Subject: [ruby-core:19176] Re: [Feature #615] "with" operator

2008/10/7 Jim Weirich <jim.weirich@gmail.com>:
> But if I understand the implementation, you are not intercepting the
> messages.  They still go to the original object.  All you've done is
> redefine the messages.  How do you plan to redirect them to the object given
> in the 'with' statement?

Maybe I see it too simplistically, but if all that's wanted in this
discussion is a possibility to get access to the outer scope, then all
you have to do is to capture it in a local variable:

  def with( obj, &blk )
    obj.instance_eval( &blk )
  end

  outer_self = self
  with "sample" do
    puts "inner self: #{self.class} #{self}"
    puts "outer self: #{outer_self.class} #{outer_self}"
  end

which results in

  inner self: String sample
  outer self: Object main

> When doing a DSL for (primarily)
> non-programmers, I have no problems going the instance_eval route.  When
> writing a library to be used by programmers, I prefer straightforward
> semantics that can easily reasoned about.

I think using instance_eval in the way shown above you get both: an
easy to use syntax for end-users and access to the outer scope for
programmers, plus straightforward semantics.

BTW: I would love to be able to uninclude modules, but I think it
isn't needed for this use case.

Regards,
Pit