From: Mike Novecento <mike.novecento@...>
Date: 2005-09-16T12:41:34+09:00
Subject: "unless" keyword

Ok guys, you convinced me: Ruby is the way to go. I have been reading
online for a few hours now, and it looks simply fantastic (especially
with Ruby on Rails).
I am so excited, I have been programming for years, and never thought
it could be so fun.

I have a first question. Looking at some code online, I have seen this
line of code from a the site of pragmatic programmer:

errors.add(:price, "should be positive") unless price.nil? || price >
0.0

I understand that it is required to validate that a price is strictly
positive.
My question, maybe very easy, is... how does it exactly work?

I thought it should be "ADD ERROR unless NOT NIL AND PRICE > 0.0"...
why he uses (OR) ||? Maybe I am missing the logic of the keyword
"unless". I feel dumb :-)

Thanks in advance,
Mike.