module InheritanceIntegerType
  module Extensions
    extend ActiveSupport::Concern
    module ClassMethods

      def integer_inheritance=(val)
        self._inheritance_mapping[val] = sti_name_without_integer_types
      end

      def find_sti_class(type_name)
        lookup = self._inheritance_mapping[type_name.to_i]
        lookup ? super(lookup) : super
      end

      def sti_name_with_integer_types
        klass = sti_name_without_integer_types
        self._inheritance_mapping.key(klass) || klass
      end
    end

    included do
      class << self
        def _inheritance_mapping
          @_inheritance_mapping ||= (superclass == ActiveRecord::Base ? {} : superclass._inheritance_mapping.dup)
        end

        def _inheritance_mapping=(val)
          @_inheritance_mapping = val
        end

        def merge_mapping!(mapping)
          conflicts = _inheritance_mapping.keys & mapping.keys
          raise ArgumentError.new("Duplicate mapping detected for keys: #{conflicts}") if conflicts.any?

          _inheritance_mapping.merge!(mapping)
        end

        alias_method_chain :sti_name, :integer_types
      end
    end

  end
end

module InheritanceIntegerType
  module Extensions
    extend ActiveSupport::Concern
    module ClassMethods

      def integer_inheritance=(val)
        self._inheritance_mapping[val] = sti_name_without_integer_types
      end

      def find_sti_class(type_name)
        lookup = self._inheritance_mapping[type_name.to_i]
        lookup ? super(lookup) : super
      end

      def sti_name_with_integer_types
        klass = sti_name_without_integer_types
        self._inheritance_mapping.key(klass) || klass
      end
    end

    included do
      class << self
        def _inheritance_mapping
          @_inheritance_mapping ||= (superclass == ActiveRecord::Base ? {} : superclass._inheritance_mapping)
        end

        def _inheritance_mapping=(val)
          @_inheritance_mapping = val
        end

        def merge_mapping!(mapping)
          conflicts = _inheritance_mapping.keys & mapping.keys
          raise ArgumentError.new("Duplicate mapping detected for keys: #{conflicts}") if conflicts.any?

          _inheritance_mapping.merge!(mapping)
        end

        alias_method_chain :sti_name, :integer_types
      end
    end

  end
end

--- 
+++ 
@@ -21,7 +21,7 @@
     included do
       class << self
         def _inheritance_mapping
-          @_inheritance_mapping ||= (superclass == ActiveRecord::Base ? {} : superclass._inheritance_mapping)
+          @_inheritance_mapping ||= (superclass == ActiveRecord::Base ? {} : superclass._inheritance_mapping.dup)
         end
 
         def _inheritance_mapping=(val)
Copy parents' mappings instead of accidentally sharing.
