mongo_mapper.rb

begin
  # require only what we need from newer versions of active_support (>= 3.0)
  require 'active_support/core_ext/class'
  require 'active_support/core_ext/object'
  require 'active_support/core_ext/module'
  require 'active_support/core_ext/hash'
rescue LoadError
  # support older versions of active_support
  require "active_support/all"
end

begin
  # prefer active_model if it exists
  require "active_model"
rescue LoadError  
  # revert back to validatable and other gems
  require 'validatable'
end