From: Robert Klemme <bob.news@...>
Date: 2006-03-10T18:18:44+09:00
Subject: Re: [Newbie] Immutable objects

Einar wrote:
> Thanks - this is starting to feel like playing an adventure game where
> the map of the terrain becomes visible as I explore it (or rather: as
> you tell me about it). It looks like symbols are appropriate here. I'm
> thinking the same might be the case for rank (e.g. "card value" from 2
> up to ace). It might look weird for the numeric values (e.g. :2 or :3
> - which might not even be legal? but then :two and :three would), but
> not so for e.g. :jack or :queen.

Alternatively you could use constants

module Deck
  JACK = "jack".freeze
  QUEEN = "queen".freeze
  ...
end

But IMHO symbols are more elegant here.  OTOH you can define a specialized
class for this which also holds numeric values

module Deck
  CARD = Struct.new :name, :value

  def self.card(name, val)
    CARD.new(name.freeze,val).freeze
  end

  QUEEN = card "queen", 10
  JACK = card "jack", 11
  ACE = card "ace", 100
  ...
end

> I'm a bit ambivalent on the strictness issue. I buy your arguments for
> a) simplicity and b) testing over typing (Bruce Eckel wrote an article
> on that, which made a lot of sense to me). At the same time, I'm still
> carrying scars from having a few leaks in the abstractions for a data
> access API I wrote in my previous job...

But these are the things that make us learn.  :-)

Kind regards

    robert