From: Dan Croak <dan.croak@...>
Date: 2007-08-10T06:29:59+09:00
Subject: Re: Using the spaceship operator to compare nil?

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... :/

  def assert_ordered_by(attribute, collection, direction)
    collection = assigns["#{collection.to_s}"]
    return true if collection.length < 2
    collection.sort do |a, b|
      if a.nil? && !b.nil?
        return false if direction.include?(">") # nil cannot be
greater than anything except another nil
      elsif b.nil? && !a.nil?
        return false if direction.include?("<") # nil cannot be
greater than anything except another nil
      elsif !a.nil? && !b.nil?
        assert a.send(attribute).send(direction, b.send(attribute))
      elsif a.nil? && b.nil?
        return true
      end
    end
  end