From: Niklas Frykholm <r2d2@...>
Date: 2002-06-07T07:53:30+09:00
Subject: Re: Getting a reference to the object which called a method

[Mathew Johnston]:
> Hmm :) What I'm trying to do is ensure that only the object which
> created another object can call it's methods. For example, object A
> instantiates object B. In object B's initialize method, I would set an
> object variable (@creator), referencing the object that called .new. On
> method calls, I would "raise 'Method called by non-creator' if [insert
> method to get ref to caller object].id == @creator.id"
> 
> Is there another way to do this?

I would probably do this by creating a proxy to the object with a safe
interface. Something like this:

	class RealClass
		def initialize
			...
		end

		def safe_method
			...
		end

		def dangerous_method
			...
		end
	end

	class SafeProxy
		def initialize(real_object)
			@real_object = real_object
		end

		def safe_method
			@real_object.safe_method
		end
	end

The creator object a would create b with

	b = RealClass.new(...)

It would keep this reference (which allows full access to b) to itself.
When it wanted to give other objects a reference to b, it would give them

	SafeProxy.new(b)

Which would ensure that the other classes could only access the safe
methods in b.

// Niklas