module ActiveFedora::Model

def self.class_exists?(class_name)
  return false if class_name.empty?
  klass = class_name.constantize
  return klass.is_a?(Class)
rescue NameError
  return false
end

def self.from_class_uri(model_value)
  unless class_exists?(model_value)
    ActiveFedora::Base.logger.warn "'#{model_value}' is not a real class" if ActiveFedora::Base.logger
    return nil
  end
  ActiveFedora.class_from_string(model_value)
end