virtus-weirdness.rb

require "virtus"

class JsonModel
  include Virtus
end

class Node < Virtus::Attribute::Object
  attr_reader :type

  class << self
    def [](type)
      raise ArgumentError, "Child nodes may only be other JsonModel classes" unless type <= JsonModel

      @generated_class_map       ||= {}
      @generated_class_map[type] ||= Class.new(self) do
        default lambda { |m, a| type.new }

        define_method :type do
          type
        end

        define_method :coerce do |value|
          value.kind_of?(Hash) ? type.new(value) : value
        end
      end
    end
  end
end

class ChildModel < JsonModel
end

class ParentModel < JsonModel
  attribute :child,  Node[ChildModel]
  attribute :string, String
end

# This should be String, but it's a descendant of Node??
puts ParentModel.attributes[:string].class.ancestors.inspect

The bug for this is in solnic/virtus#26 .. and it is now resolved.

(Added for posterity for anyone that comes across this in google)