compute_class

# File activerecord/lib/active_record/reflection.rb, line 415
      def compute_class(name)
        if polymorphic?
          raise ArgumentError, "Polymorphic associations do not support computing the class."
        end

        msg =           Rails couldn't find a valid model for #{name} association.          Please provide the :class_name option on the association declaration.          If :class_name is already provided, make sure it's an ActiveRecord::Base subclass..squish

        begin
          klass = active_record.send(:compute_type, name)

          unless klass < ActiveRecord::Base
            raise ArgumentError, msg
          end

          klass
        rescue NameError
          raise NameError, msg
        end
      end