From: Paul Mckibbin <pmckibbin@...>
Date: 2011-02-11T01:02:22+09:00
Subject: Re: attr_reader vs Objects and Attributes

Mike Onofrietto wrote in post #980715:
> Hello World.
> This is my first forum membership, and first post.
> I am learning Ruby.
> It seems to be a very elegant an encompassing OO language.
> I'm reading Thomas & Hunt: Classes, Objects, and Variables on-line.
>
> See attached.
>
> Regarding the following by the authors, and attached I see no
> correlation.
> However I've had very good results with attr_accessor.
> Please help.
>
In your test code, and the attachment, you don't have an initialize 
function, which is defined in the first page of the book:

i.e.

class Song
  def initialize(name, artist, duration)
    @name     = name
    @artist   = artist
    @duration = duration
  end
end

The way Ruby works is that if this is defined, even if you have a new 
class block i.e.

class Song
  def name; @name; end
  def artist; @artist; end
  def song; @song; end
end

that doesn't overwrite the previous definition. It EXTENDS it. So now 
your class should be (in memory anyway) equivalent to:

class Song
  def initialize(name, artist, duration)
    @name     = name
    @artist   = artist
    @duration = duration
  end

  def name; @name; end
  def artist; @artist; end
  def song; @song; end
end

Without the initialization, you are called the base class 
Object.new(*arr) method, which will not assigned any class variables for 
you, regardless of whether you use attr_x methods or not.

Mac.

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