From: Mikael Brockman <mikael@...>
Date: 2004-08-16T22:29:26+09:00
Subject: Re: returning symbols

Daniel Cremer <daniel@danielcremer.com> writes:

> I want to write a method to store a list of some instance variables in
> an Array that will later be run through to access their data. Normally
> in another language I would do this by passing them by reference when I
> store them into the Array. 
> 
> Using the object_id doesn't work because that's to the object the
> variable is pointing to and this may change.  
> So, to sum it up:
> 
> Is there a way to get variables to return their symbol so you can access
> what they will be referencing in the future ?
> 
> thanks,
> Daniel

It's kind of a hack, and you should avoid using it, but

| class Box
|   def initialize (&accessor)
|     @accessor = accessor
|   end
| 
|   def set! (new)
|     @accessor.call new
|   end
| 
|   def get
|     @accessor.call
|   end
| end
| 
| class Object
|   def box (variable)
|     Box.new do |*value|
|       if value.empty?
|         instance_variable_get variable
|       else
|         instance_variable_set variable, value.first
|       end
|     end
|   end
| end

> foo = Foo.new
=> #<Foo:0x402f94c4 @a=5>
> box = foo.box(:@a)
=> #<Box:0x402f68dc @accessor=#<Proc:0x4030f530@./boxes.rb:18>>
> box.get
=> 5
> box.set! 10
=> 10
> box.get
=> 10
> foo.instance_variable_get(:@a)
=> 10