[PATCH] Abstract class and Inheritance fix

Also see Patch #5704

(In [6013]) Subclasses of an abstract class work with single-table inheritance. References #5704, closes #7284.

STI is incorrectly disabled in situations like:

class AbstractClass < ActiveRecord::Base
class ConcreteClass1 < AbstractClass
class ConcreteClass2 < AbstractClass

what's wrong with

def self.descends_from_active_record? # Better method name: no_sti?
  self.abstract_class? || !columns_hash.include?(inheritance_column)
end

, setting the type field for AR descendants as well?

Hey,

This is the same issue i fixed in the past, sadly it was overwritten by a later changeset (including the test). I will create an other changeset (with the test).

I suggest there should be an investigation on how this issue could have been reintroduced.

Ok,

So apparently the fix is reintroduced with Rails 2.0, but in the older 1.2.x series the patch has disappeared.

I suggest that bitsweat applies changeset [6013] to the 1.2.x branch in the next maintenance release.

I'm seeing the problem on 2.0.1, not 1.2.6. It seems STI is only set up to handle class chains, not arbitrary class hierarchies, some classes being abstract. If there's a concrete class on another chain, it won't be detected for the purposes of enabling STI.

In the AR unit tests, you could add a GroupOfCompanies concrete class that descends from AbstractCompany. The aim would be to ensure that the type field gets set on GroupOfCompanies objects, to differentiate them from Company objects.

I'm now running 2.0.1 with the monkey patch

class ActiveRecord::Base
  def self.descends_from_active_record?
    superclass == self || !columns_hash.include?(inheritance_column) || self.abstract_class?
  end
end

but this breaks many AR unit tests. But is it just that the test conditions should be changed?

Bert, I don't yet understand why your original patch was needed. Could you please explain what it fixed, and how you think STI should work. What's wrong with the my code above for deciding whether to put something in the inheritance field? Table names seem to be correctly determined.

Make that monkey patch

class ActiveRecord::Base
  def self.descends_from_active_record?
    superclass == ActiveRecord::Base || !columns_hash.include?(inheritance_column) || self.abstract_class?
  end
end