class Level1
  include Mongoid::Document

  embeds_many :level2s
end

class Level2
  include Mongoid::Document

  embedded_in :level1
  embeds_many :level3s
end


class Level3
  include Mongoid::Document

  embedded_in :level2

  field :name, :type => String
end

Level1.delete_all

level1 = Level1.new
level1.level2s.new
level1.level2s.last.level3s.new :name => 'level 3'
level1.save
puts "Level 3 name: #{Level1.last.level2s.last.level3s.last.name}"

level1 = Level1.last
level1.level2s.last.level3s.last.name = 'level 3 updated'
level1.save
puts "Level 3 name: #{Level1.last.level2s.last.level3s.last.name}"

level1 = Level1.last
level1.level2s.last.level3s.last.update_attribute :name, 'level 3 updated again'
puts "Level 3 name: #{Level1.last.level2s.last.level3s.last.name}"

Level 3 name: level 3
Level 3 name: level 3
Level 3 name: level 3