From: Logan Capaldo <logancapaldo@...>
Date: 2006-07-14T12:46:10+09:00
Subject: Re: "Self" Reference


On Jul 13, 2006, at 7:00 PM, Marcin Miel��y��ski wrote:

> Nathan Olberding wrote:
>> Is it possible to define new classes that behave like standard  
>> datatypes when an instance is referred to? For example:
>> class ListOfBuddies
>>     def initialize
>>         self = []
>>         self.push(Guy.new(name))
>>     end
>> end
>> buddy_list = ListOfBuddies.new
>
> Then, definitely, inheritance is the right choice:
>
> class ListOfBuddies < Array
>      def initialize
>         self.push(Guy.new(name))
>      end
> end
>
> buddy_list = ListOfBuddies.new
>
>
> lopex
>


Ehhh, I wouldn't necessarily choose inheritance. It depends on what  
he's doing but ListOfBuddies doesn't strike as having an isa  
relationship with an Array. I personally would choose delegation:

Couple of ways to this:

require 'delegate'
class ListOfBuddies < DelegateClass(Array)
   def initialize
     __setobj__([])
     push Guy.new(name)
   end
end

or

require 'forwardable'
class ListOfBuddies
   extend Forwardable

   def initialize
     @list = []
     push Guy.new(name)
   end

   def_delegators :@list, :push, :[]
end

The last is my personal favorite. You get to pick exactly what  
methods get delegated to the delegate and unlike inheritance you  
don't accidently pull in stuff that could possibly kill your  
invariants. (esp. with core classes like Array, they have a _lot_ of  
methods).