From: matt@... (matt neuburg)
Date: 2009-03-31T10:49:55+09:00
Subject: Re: When to use instance variables @

Steve Dogers <stevedogers@gmail.com> wrote:

> Hi, I have a couple questions about instance variables in Ruby.
> 1) do i need to declare them at the top of my class file - I do
> understand the accessors are automatic but I'm not sure if I can just
> pull a @product in the middle of a function

No, nor can you! Code that looks like it is declaring them isn't. A
common beginner mistake is illustrated by this experimented:

class C
  @greeting = "howdy" # doesn't do what you might suppose
  def greet
    puts @greeting
  end
end
C.new.greet #=> nil # surprise!

The @greeting that looks like it's being declared in the second line is
not, in fact, the instance variable mentioned inside the "greet" method.
(It is something else entirely - a "class instance variable".) m.

-- 
matt neuburg, phd = matt@tidbits.com, http://www.tidbits.com/matt/
Leopard - http://www.takecontrolbooks.com/leopard-customizing.html
AppleScript - http://www.amazon.com/gp/product/0596102119
Read TidBITS! It's free and smart. http://www.tidbits.com