From: FirstName Surname <lists@...>
Date: 2013-02-06T05:17:20+09:00
Subject: using an instance variable inside a method

Hello.

I'm learning ruby 1.9 by reading the book "Programming Ruby 1.9
The Pragmatic Programmers’ Guide"

Actually i'm on the page 57 and i think something is wrong. Let's show
the involved code :

#---
# Excerpted from "Programming Ruby",
# published by The Pragmatic Bookshelf.
# Copyrights apply to this code. It may not be used to create training
material,
# courses, books, articles, and the like. Contact us if you are in
doubt.
# We make no guarantees that this code is fit for any purpose.
# Visit http://www.pragmaticprogrammer.com/titles/ruby3 for more book
information.
#---
class BookInStock

  attr_reader   :isbn
  attr_accessor :price

  def initialize(isbn, price)
    @isbn  = isbn
    @price = Float(price)
  end

  def price_in_cents
    Integer(price*100 + 0.5)
  end
  # ...
end
book = BookInStock.new("isbn1", 33.80)
puts "Price          = #{book.price}"
puts "Price in cents = #{book.price_in_cents}"


About the method price_in_cents, i think it should be written like that
instead :

  def price_in_cents
    Integer(@price*100 + 0.5)
  end

Simply because unless i'm really missing something, "price" is a class
attribute after all there, it seems that in this case the "@" is
implicit, but that doesn't look the appropriate way to write it, right ?
Anyway i've tested with and without the "@", the result is the same.

So is this a common practice in ruby or what ?

Thx for reading.

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