From: Tobias DiPasquale <anany@...>
Date: 2001-12-03T21:55:11+09:00
Subject: [ruby-talk:27345] not as easy as the last one...

Hi all,

Another question for the Ruby-omniscient ruby-talk ML folk! Joy!! 
Anyway, here's one a little more difficult than my last one (I think, 
anyway): is there a way for me to create methods in a class that can 
only be called by an object of another class? (not even itself or other 
objects of it's class)

What I am trying to do is this: imagine that the SimpleObject class had 
two methods, called _inc and _dec. Now imagine that no instance on 
SimpleObject or any of it's descendents could fire those methods. Nor 
could any other living object in the current running program (or any) 
fire these methods, EXCEPT a singleton instance of another class, called 
Container, in which the instances of SimpleObject happen to be 
"contained". (pun intended; they are just housed in a hash inside Container)

Here's an outline:

<dream_snippet>
class Container
   include Singleton

  def inc(obj)
   if obj.instance_methods.include?('_inc') && \
     obj.kind_of?('SimpleObject')
    obj._inc  # increment this object's ref count
   end
  end #inc

#-------problem area-----------
  def caller_valid?(*args)  # who knows what this method should take?
   # make sure that the Container instance is the calling object
   # or return false
  end #caller_valid?
#------------------------------

end #Container

c = Container.instance

class SimpleObject

  def initialize
   @refCount = 0
  end #initialize

  attr_reader :refCount

  def _inc
   refCount += 1 if c.caller_valid?(<<???>>)
  end #_inc

  def _dec
   refCount -= 1 if c.caller_valid?(<<???>>)
  end #_dec

end #SimpleObject

x = SimpleObject.new
x._inc
x.refCount  # => 0

c.inc(x)
x.refCount  # => 1

</dream_snippet>

Any chance of doing this? If not, anyone know of a workaround? Thanks in 
advance!!

-- 

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<< Tobias DiPasquale >>
-=[ Solaris Systems Administrator ]=-
Villanova University ECE Dept.
mailto: anany@ece.vill.edu
-=[ Applications Engineering Consultant ]=-
BCS Solutions, Inc.
mailto: tdipasquale@bcssinc.com
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