rails--rails/activerecord/test/models/customer.rb

class Customer < ActiveRecord::Base
  composed_of :address, :mapping => [ %w(address_street street), %w(address_city city), %w(address_country country) ], :allow_nil => true
  composed_of(:balance, :class_name => "Money", :mapping => %w(balance amount)) { |balance| balance.to_money }
  composed_of :gps_location, :allow_nil => true
end

class Address
  attr_reader :street, :city, :country

  def initialize(street, city, country)
    @street, @city, @country = street, city, country
  end

  def close_to?(other_address)
    city == other_address.city && country == other_address.country
  end

  def ==(other)
    other.is_a?(self.class) && other.street == street && other.city == city && other.country == country
  end
end

class Money
  attr_reader :amount, :currency

  EXCHANGE_RATES = { "USD_TO_DKK" => 6, "DKK_TO_USD" => 0.6 }

  def initialize(amount, currency = "USD")
    @amount, @currency = amount, currency
  end

  def exchange_to(other_currency)
    Money.new((amount * EXCHANGE_RATES["#{currency}_TO_#{other_currency}"]).floor, other_currency)
  end
end

class GpsLocation
  attr_reader :gps_location

  def initialize(gps_location)
    @gps_location = gps_location
  end

  def latitude
    gps_location.split("x").first
  end

  def longitude
    gps_location.split("x").last
  end

  def ==(other)
    self.latitude == other.latitude && self.longitude == other.longitude
  end
end