From: Gregory Brown <gregory.t.brown@...>
Date: 2007-08-10T06:39:48+09:00
Subject: Re: Using the spaceship operator to compare nil?

On 8/9/07, Dan Croak <dan.croak@nationalgazette.org> wrote:
> I forgot to mention that this is called, for example, with:
>
> assert_ordered_by :last_name, :users, "<="
>
> I'm also moving away from using the spaceship operator into
> conditional logic land because I was having difficulty dealing
> (mentally) with comparing nil to various types (dates, strings,
> integers, etc.). Here's the latest non-working code... :/

Try this:

has_nil, doesnt = collection.partition { |r| r.send(attribute).nil? }

you can then sort only the ones that have a meaningful sort value and
then rejoin as needed based on the direction, e.g. for one directed
you want:

doesnt.sort + has_nil

and for another you want

has_nil + doesn't.sort

hope that helps.  Excuse the incomplete code :)