gistfile1.rb

require 'rubygems'
require 'couchrest'

class Doc < CouchRest::ExtendedDocument
  property :normal_property
  property :casted_model, :cast_as => 'CastedModel'
end

class CastedModel < Hash
  include CouchRest::CastedModel
end

doc = Doc.new
[:normal_property, :casted_model].each do |prop|
  print "#{prop} is "
  puts doc.send(prop).nil? ? "nil" : "a #{doc.send(prop).class}"
end