From: ara.t.howard@...
Date: 2006-03-12T05:09:42+09:00
Subject: Re: attribute setters for instance variables

On Sun, 12 Mar 2006 eliben@gmail.com wrote:

> Hello,
>
> The Pickaxe book presents the following example:
>
> class Incorrect
>  attr_accessor :one, :two
>  def initialize
>    one = 1
>    self.two = 2
>  end
> end
>
> obj = Incorrect.new
>
> p obj.one
> p obj.two
>
> The first thing printed is 'nil' and not '1' since "one = 1" assigns to
> a local variable of method initialize instead of the instance variable.
> So far it's clear.
> Now, they propose a solution: to use self.one instead of just one.
> Won't be using @one simpler and also correct ? What am I missing ?

   def one= arg
     log{ "somthing about one" }
     validate{ arg }
     notify_observers :one, arg
     @one = arg
   end

just a few examples.

this become even more true when the number attribues increases since you can

   class C
     ATTRIBUTES = %w[ one two three four five six seven ]
     def initialize kws = {}
       kws.each{|kw, val| send "#{ kw }=", val}
     end
   end

in one line even if the number of attributes is huge.


i'd also argue that the simplest thing is to simply make the getter take and
optional argument so one can do

   def initialize
     one 1
     two 2
   end

but that's a matter of taste.

hth - cheers.

-a

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