module URLAttributes

Use:

# Model with string attributes called 'checkout_url' and 'homepage_url'
class Example < ActiveRecord::Base

  url_attribute :checkout_url, :homepage_url

end

The above will cause the attribute 'url' to be validated with URLValidator (NB the validation will pass if no URL is present), and it will have 'http://' added it to it if it's not provided.