Optional belongs_to relationship in Ruby

I'm migrating an application over to ROR from PHP that defines an object, let's call it a Document that can be created by a User who is either a registered user of the application, or an anonymous user who only gives their email address (in this case without an associated User account). There is no requirement for a visitor to create a User account, but they should still have the ability to create a Document.

In my model, I am first led to create the Document model that references the user with a belongs_to association. This however is not always the case. In pure SQL and PHP this is not hard, although it comes with it's own challenges, but I would like to model this in the "purest" Ruby/Rails way.

If a visitor d开发者_开发问答oes not have an associated User, their email address will be stored directly against the Document object.

To start the discussion, here are the snippets for each model.

# user.rb
class User < ActiveRecord::Base
  has_many :documents
end

# document.rb
class Document < ActiveRecord::Base
  attr_accessible :title, :description, :email_address

  belongs_to :user
end

My goal is to be able to retrieve all user documents using the standard dot notation:

user.documents

And to also check for the reverse relationship to see if the document belongs to a User or if it contains an email address.

if document.user.nil? ...

if document.email_address.nil? ...

I have read up on the has_one relationship but am not sure if this is the right path to go down.

Any help or suggestions would be appreciated, thanks!

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You might want to consider making the User class more flexible so it supports anonymous users and only stores the email address.

It might make your code a bit cleaner.