If you have an embeds_one relationship that at some point gets set to nil, calling #as_document on the model will cause a NoMethodError. I ran into this where my destroy callback ended up calling #as_document and I got this error:

p = Person.new(title: "Sir")
p.build_name(first_name: "James")
p.save
p.name = nil
p.save
p.reload

# This line will throw a NoMethodError
p.as_document

This patch fixes it and adds a spec.

Also, in doing this, I realized that the "as_document" doesn't update until the document is re-pulled from Mongo. That is, in my above example if you don't call p.reload, then p.as_document will return {{{ "name" :

}}} even if the document is saved. @durran, is this expected behavior? Seems like a bug but wanted to ask you first.