add (DataMapper::Validate::ValidationErrors)

    # File lib/dm-validations/validation_errors.rb, line 64
          def add(field_name, message)
            # see 6abe8fff in extlib, but don't enforce
            # it unless Edge version is installed
            if message.respond_to?(:try_call)

              # DM resource
              message = if resource.respond_to?(:model) && resource.model.respond_to?(:properties)
                message.try_call(resource, resource.model.properties[field_name])
              else
                # pure Ruby object
                message.try_call(resource)
              end
            end
            (errors[field_name] ||= []) << message
          end