mongo_example1.rb

class Address
  include MongoMapper::EmbeddedDocument
  key :address
  key :city
  key :country
end

class Customer
  include MongoMapper::Document
  key :name, :required => true
  many :addresses
end

customer = Customer.new(:name => "Felipe Coury")
customer.save #=> true

address = Address.new(:address => "203 Main St.", :country => "Brazil")
address.save #=> NoMethodError: undefined method ‘save’ for #<Address":0x123a248>

customer.addresses << address
customer.save #=> true