From: jim@...
Date: 2004-11-12T05:21:18+09:00
Subject: Re: ruby idiom for attribute definition?

* Dave Thomas <dave@pragprog.com> [2004-11-12 04:46:04 +0900]:

> Exactly - that's what made me suggest it. A class with a large number 
> of attr_accessors is not really an encapsulated class, so it felt to me 
> that a Struct would be more appropriate.
 
 Below is an example that speaks to your comment about structs not being
 generally useful for inheritance:

    S = Struct.new(:a, :b)

    class C < S
      attr_accessor :c, :d

      def  do_something_clever
        "#{a} : #{b} | #{@c} : #{@d}"
      end
    end

The problem is that I have to know which IV came from C
and which came from Struct. I suppose that I could use
the getter/setter methods for all IV's, but I thought
that @c was avoiding a function call that 'c' was making,
and I would like to avoid that.

 Dave, earlier you suggested that Structs cheat. Well, 
 I suppose I could try to out cheat the struct with:

 class C < S
   attr_accessor :a, :b, :c, :d
   def ...
   end
 end

Now I get all the benefits of Struct for :a and :b,
but the problem is that I am violating DRY.

-- 
Jim Freeze