From: dblack@...
Date: 2007-01-03T18:20:59+09:00
Subject: Re: Pickaxe question: "... on the way to true Ruby mastery."

Hi --

On Wed, 3 Jan 2007, jeffz_2002@yahoo.com wrote:

> Hey Andre, I believe the line reads slightly differently than you've
> interpreted ... some more info (note: I still don't have the answer):
>
> ||= is actually a ruby idiom to initialize a variable if it's nil.  In
> other words, "a ||= 6" actually means "a = 6 if a.nil?" or "a = 6
> unless a".  (sorry if I'm lecturing)  In other words, if @foo really
> *is* a value, and it really *is* nil, I think the function call is
> going to be made no matter what ... but again, this is a bit over my
> head at present.
>
> So, converting __#{id.to_i}__ to something more readable, like "foo",
> this: (@foo ||= [foo(*a, &b)] )[ 0 ]
>
> should be the same as the more verbose:
>
> if @foo
>  return @foo[ 0 ]   # Still not sure why the [0] is required!
> else
>  return foo( *a, &b )    # the 0th index of the single array
> end

It's more like:

   if @foo
     return @foo[0]
   else
     @foo = [foo(*a, &b)]
     return @foo[0]
   end

or, more simply,

   @foo = [foo(*a, &b)] unless @foo
   return @foo[0]

In other words, @foo gets assigned to, if it's nil to start with.


David

-- 
Q. What is THE Ruby book for Rails developers?
A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
    (See what readers are saying!  http://www.rubypal.com/r4rrevs.pdf)
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)