From: itsme213 <itsme213@...>
Date: 2005-04-03T02:34:44+09:00
Subject: Re: how to simulate self-style delegation [SuperHash]


"Saynatkari" <ruby-ml@magical-cat.org> wrote in message

> Perhaps I'm missing a crucial point here. Should a B 'be' an A
> in the normal is_a sense? Should B have access to A's state?
> Something more than what SimpleDelegator offers?

SELF-style delegation is for "inheriting" at the _object_ level. It lets me
dynamically change the object that b1 delegates to.
    b1 = B.new
    b1.delegate_to(a1)
    ...stuff
    b1.delegate_to(a2)

So
    class B < A; end
does not help.

SimpleDelegator simply forwards missing methods, it does not provide the
binding of self that I am looking for. Here is another example with desired
behavior at the end.

class Role
  def initialize(type)
    @type = type
  end
  def name
    "unbound"
  end
  def describe
    "I am #{self.name}, a #{@type}"
  end
end

PM = Role.new("Project Manager")
GA = Role.new("Graphic Artist")

class Person
  attr_accessor :name
  def delegate_to
    ?? method_missing and self_binding magic here
  end
end

JOE = Person.new
JOE.name = "Joe"

JOE.delegate_to(PM)
JOE.describe #=> "I am Joe, a Project Manager"

JOE.delegate_to(GA)
JOE.describe #=> "I am Joe, a Graphic Artist"

Hope that is more clear. Maybe this is not possible in Ruby ... but I just
got a pointer to _evil_ ruby, perhaps that might have something?