From: Brian Candler <B.Candler@...>
Date: 2007-04-05T06:26:37+09:00
Subject: Re: nil? and non-existent objects

On Thu, Apr 05, 2007 at 04:25:23AM +0900, Fran?ois Montel wrote:
> Why is it that the nil? method can sometimes be called on an object that
> doesn't exist, and other times will return an error. Under what
> circumstances can you call the nil? method on a non-existent object?
> 
> Consider:
> 
> >> puts x = 1 if x.nil?
> => 1
> >> puts ???z is not defined??? if z.nil?
> => NameError: undefined local variable or method ???z???

Maybe easier to understand if you consider this:

if false
  x = 0
end

puts x.inspect   # => nil

When the file is *parsed*, the assignment "x = 0" flags "x" as a
local variable from that point onwards within the scope. This is true
whether or not it is actually executed; it's a parse-time decision as to
whether "x" is a local variable or a method call with implicit receiver.

Regards,

Brian.