From: Sebastian Hungerecker <sepp2k@...>
Date: 2008-06-30T17:41:56+09:00
Subject: Re: Newby question about Variables

Sean Murphy wrote:
> Instant Variables I am completely mystified on their purpose and their
> difference between a local variable.

They're called instance variables, not instant variables. And they're called 
that because they're specific to an instance of a class (i.e. to an object).
For example take the following class:
class Foo
  def initialize(bar)
    @bar = bar
  end
  def bar
    @bar
  end
end
f1 = Foo.new(5)
f2 = Foo.new(4)
f1.bar #=> 5
f2.bar #=> 4

So here you have two instances of the class Foo. One instance has the value 5 
stored in the instance variable @bar, the other one the value 4. As long as 
f1 and f2 exist you will be able to access their values for @bar via the bar-
method. If @bar were a local variable, it would disappear after the initialize 
method is done and thus would not be accessible from the bar method. If @bar 
was a global variable, it would not be object-specific, so f1.bar and f2.bar 
would return the same thing.

HTH,
Sebastian
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