From: Patrick Hurley <phurley@...>
Date: 2006-05-04T23:05:50+09:00
Subject: Re: A question about attr_reader

On 5/4/06, Akbar Pasha <akbarpasha@gmail.com> wrote:
> Hi All,
>
> I am just going through the pickacxe book and have a question about
> attr_reader. Here is the sample class.
>
> class Song
>     def initialize(name, artist, duration)
>         @name = name
>         @artist = artist
>         @duration = duration
>     end
> end
>
> It says I can do the following-
>
> class Song
>     def name
>         @name
>     end
>     def artist
>        @artist
>    end
>     def duration
>         @duration
>     end
> end
>
> OR
>
> I can do the following-
>
> class Song
>     attr_reader :name, :artist, :duration
> end
>
> This is fine, but it says "The corresponding instance variables, @name,
> @artist, and @duration, will be created automatically" (on Page 31) about
> attr_reader. I kinda thought that those variables are already created when
> "initialize" function is called. If I comment the initialize function and
> run it - I get an error.
>
> So what does the author mean by that?
>
> Thanks in advance,
>
> ::akbar
>
>

Maybe this will help clarify:

class Foo
   attr_reader :bar

   def go_to_the_bar
     @bar = 'anytime'
   end
end

foo = Foo.new
p foo.bar
foo.go_to_the_bar
p foo.bar

There is no error, accessing the instance variable @bar, from the
reader (it has a value of nil) -- it is created on the fly. I am
guessing you commented out your initialize, but were still calling the
constructor with parameters?

pth