Poor-man's Embedded Value

ev.rb

class User
  include DataMapper::Resource

  property :id,                     Serial
  property :username,               String, :required => true, :unique => true
  property :address_street_address, String
  property :address_location,       String
  property :address_subdivision,    String
  property :address_country,        String

  def address
    @address ||= Address.new(self, 'address')
  end

  def address=(new_address)
    new_address.each { |key, value| address[key] = value }
  end

end

class Address
  def initialize(resource, prefix)
    @resource = resource
    @prefix   = prefix
  end

  def [](key)
    send(key)
  end

  def []=(key, value)
    send("#{key}=", value)
  end

  def respond_to?(method, include_private = false)
    @resource.respond_to?(proxy_method_for(method)) || super
  end

  def method_missing(method, *args, &block)
    if respond_to?(method)
      @resource.send(proxy_method_for(method), *args, &block)
    else
      super
    end
  end

private

  def proxy_method_for(method)
    "#{@prefix}_#{method}"
  end

end

__END__

# the above will allow code like the following to work as expected:

user = User.create(
  :username => 'dkubb',
  :address  => {
    :location    => 'Mission',
    :subdivision => 'BC',
    :country     => 'Canada',
  }
)

puts user.address.location  # => "Mission"