class NestedFieldTest include Mongoid::Document field :title, :type => String belongs_to :field_test, :inverse_of => :nested_field_tests belongs_to :another_field_test, :inverse_of => :nested_field_tests include Mongoid::Timestamps has_one :comment, :as => :commentable, :autosave => true accepts_nested_attributes_for :comment, :allow_destroy => true, :reject_if => proc { |attributes| attributes["content"].blank? } end