Rails STI - Prevent base class from instantiation

Question

Is there any way in a Rails STI situation to throw an error when the base class is Instantiated? Overriding initialize will do it but then that gets trickled down to the sub

Answer 1

The answer by John Topley is actually wrong. Setting abstract_class = true in the base class will actually cause the child classes to stop setting their type automatically. Plus, unless you set_table_name in the base class, the child classes will complain their table does not exist.

This is because the purpose of abstract_class=true is to set up inheritance when you are NOT using STI, and want to have an abstract class (class not backed by a db table) in your class hierarchy between ActiveRecord::Base and one or more model classes.

Having initialize raise is one solution, also adding validates_presence_of :type to the base class is a solution.

Note if you DO override initialize, you need to call super:

def initialize(*args)
  raise "Cannot directly instantiate an AbstractUser" if self.class == AbstractUser
  super
end