autoload_missing_constants.rb

module AutoloadMissingConstants

  # Automatically loads constants that Ruby doesn't know about when unmarshalling in the given block. This triggers
  # Rails/ActiveSupport's smart autoloading code via constantize. Adapted from cache_fu/cache_methods.rb:214
  #
  # ==== Parameters
  #
  # &block:: Unmarshalling block.
  #
  # ==== Raises
  #
  # NameError:: Constant can't be found.
  #
  def self.protect
    yield
  rescue ArgumentError => e
    raise unless e.to_s =~ /undefined class/ # unexpected error message, re-raise
    e.to_s.split.last.constantize            # raises NameError if it can't find the constant
    retry
  end

end