STI

Dynamoid supports STI (Single Table Inheritance) like Active Record does. You need just specify type field in a base class. Example:

class Animal
  include Dynamoid::Document

  field :name
  field :type
end

class Cat < Animal
  field :lives, :integer
end

cat = Cat.create(name: 'Morgan')
animal = Animal.find(cat.id)
animal.class
#=> Cat

If you already have DynamoDB tables and the type field already exists and has its own semantic it leads to a conflict. It’s possible to tell Dynamoid to use another field (even a non-existent one) instead of the type one with the inheritance_field table option:

class Car
  include Dynamoid::Document

  table inheritance_field: :my_new_type

  field :my_new_type
end

c = Car.create
c.my_new_type
#=> "Car"