compute_class

# File activerecord/lib/active_record/reflection.rb, line 462
      def compute_class(name)
        if polymorphic?
          raise ArgumentError, "Polymorphic associations do not support computing the class."
        end

        begin
          klass = active_record.send(:compute_type, name)
        rescue NameError => error
          if error.name.match?(/(?:\A|::)#{name}\z/)
            message = "Missing model class #{name} for the #{active_record}##{self.name} association."
            message += " You can specify a different model class with the :class_name option." unless options[:class_name]
            raise NameError.new(message, name)
          else
            raise
          end
        end

        unless klass < ActiveRecord::Base
          raise ArgumentError, "The #{name} model class for the #{active_record}##{self.name} association is not an ActiveRecord::Base subclass."
        end

        klass
      end