From: Dan Croak <dan.croak@...>
Date: 2007-08-10T04:20:06+09:00
Subject: Using the spaceship operator to compare nil?

Hey folks,

I have a test helper in a Rails app called assert_ordered_by

def assert_ordered_by(attribute, collection, direction)
  collection = collection.to_s
  return true if assigns["#{collection}"].length < 2
  option_one = assigns["#{collection}"][0].send(attribute)
  option_two = assigns["#{collection}"][1].send(attribute)
  assert option_one.send(direction, option_two), "#{option_one} is not
#{direction} #{option_two}"
end

It works well in all the cases I've tried thus far except when dealing
with nil. I want to teach the method to treat nil the same way SQL
treats NULL because the collections will often contain ActiveRecord
objects.

I have the idea in my head that I need to use the spaceship operator
(<=>) to do this, but am unsure about how...

Any ideas?

Thanks,
Dan Croak
http://thoughtbot.com/