mongodb/mongoid · error · Mongoid::Errors::UnknownModel

Attempted to instantiate an object of the unknown model '%{k

Error message

Attempted to instantiate an object of the unknown model '%{klass}'.

What it means

Error "Attempted to instantiate an object of the unknown model '%{klass}'." thrown in mongodb/mongoid.

Source

Thrown at lib/mongoid/factory.rb:112

      # @return [ Document ] The instantiated document.
      def instantiate_with_type(execute_callbacks)
        constantized_type.instantiate_document(
          attributes, selected_fields,
          execute_callbacks: execute_callbacks
        )
      end

      # Retrieve the `Class` instance of the requested type, either by finding it
      # in the `klass` discriminator mapping, or by otherwise finding a
      # Document model with the given name.
      #
      # @return [ Mongoid::Document ] the requested Document model
      def constantized_type
        @constantized_type ||= begin
          constantized = klass.get_discriminator_mapping(type) || constantize(type)

          # Check if the class is a Document class
          raise Errors::UnknownModel.new(camelized, type) unless constantized.respond_to?(:instantiate)

          constantized
        end
      end

      # Attempts to convert the argument into a Class object by camelizing
      # it and treating the result as the name of a constant.
      #
      # @param type [ String ] The name of the type to constantize
      #
      # @raise [ Errors::UnknownModel ] if the argument does not correspond to
      #   an existing constant.
      #
      # @return [ Class ] the Class that the type resolves to
      def constantize(type)
        camelized = type.camelize
        camelized.constantize
      rescue NameError

View on GitHub (pinned to 0da0e23d71)

When it happens

Trigger: Thrown at lib/mongoid/factory.rb:112 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mongodb/mongoid@0da0e23d71 (2026-08-23). Data as JSON: /api/errors/ca5e9571a641bd02. Report an issue: GitHub.