embeds_one – embed one document

This relation takes the standard options, which we have seen earlier: :autobuild, :as, :cascade_callbacks, :cyclic, :store_as, and so on. However, it's interesting how we can manage relations using the names of the relations.

What if we want to save the relation twice in the same parent class? For example, in the Author model, we want the permanent and current addresses. Both are Address objects. We use the name option that specifies the name of the relation in which the information would be stored. Have a look at the following code:

class Author
  include Mongoid::Document

  embeds_one :permanent_address, class_name: "Address"
  embeds_one :current_address, class_name: "Address"
end

class Address
  include Mongoid::Document

  embedded_in :author, inverse_of: :permanent_address
  embedded_in :author, inverse_of: :current_address
end

If we create an author now, MongoDB stores both the addresses under different names:

{ "_id" : ObjectId("51b42d4245db7c9535000001...