From: transfire@...
Date: 2006-07-22T22:34:02+09:00
Subject: Re: Assigning blame?


Ben Zealley wrote:
> 'allo
>
> Say I have two classes:
>
> class Bloke
> 	attr_reader :name
> 	def sellSoul(aDemon)
> 		aDemon.buySoul(self)
> 	end
> end
>
> class Demon
> 	def buySoul(aBloke)
> 		# if aBloke called the method, OK. Else, tell them where to go.
> 		puts("I bought #{aBloke.name}'s soul!")
> 	end
> end
>
> Tim = Bloke.new
> Tim.name = "Tim"
> Satan = Demon.new
> Tim.sellSoul(Satan)
>
> I would like the buySoul method to work only if the Bloke calling it is
> the same instance of Bloke named, but I can't find any way to determine
> what object called a given method. Does anyone have a suggestion?

Some might argue that you can't do thi, b/c in reality what you want to
do is flawed conceptually. Be that as it may, you're essentially asking
for the Binding.of_caller, a well known extension, but one that is far
from perfect too.  Albiet, in your case, and most cases I have ever
considered, a "self_of_caller" would suffice --the whole binding is
generally overkill. In any case, it can be done generally if you pass a
block:

  require 'facet/binding/self'  # see below for this code

  class Bloke
 	attr_reader :name
 	def sellSoul(aDemon)
 		aDemon.buySoul{self}
 	end
 end

 class Demon
 	def buySoul(&aBloke)
 		# if aBloke called the method, OK. Else, tell them where to go.
                if aBloke.binding.self == Bloke
 	  	  puts("I bought #{aBloke[].name}'s soul!")
                else
                  puts "You know were to go!"
                end
 	end
 end

T.


P.S. binding/self + binding/eval:

 class Binding

  # Returns the self in the binding context.
  def self()
    @self ||= eval( "self" )
    @self
  end

  # Evaluate a Ruby source code string (or block) in the binding
context
  def eval( str ) #='', &blk )
     Kernel.eval( str, self )
  end

 end