ActiveRecord single table inheritance - how to get root model?

Question

I have a model using single table inheritance and a concern that should work on any model.

Consider this example:

class Car
  acts_as_categorizable
end

class Suv < Car; end

module Categorizable
  def after_safe
    siblings = this.class.where(category: self.category)
    #... do something with the siblings
  end
end

Now if I have an Suv and manipulate its category, the siblings line will only find the other Suv cars in that category, but I need to find all cars in that category.

I don't want to hardcode this, so given a Suv class, I need to find its root model (Car).

For that you have to establish has_many and belongs_to relation b/w car & suvs — Muhammad Ali, May 02 '16 at 12:56
Your module has to work on non-car models as well? If not, one option would be to query the Car model `Car.where(category: self.category)`. — Uzbekjon, May 02 '16 at 13:08

score 2 · Accepted Answer · answered May 07 '16 at 11:04

2

There's actually already a method for this; base_class. So Suv.base_class should return Car, and any subclass of Suv will also return Car with this method.

answered May 07 '16 at 11:04

Andrew Schwartz

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score 0 · Answer 2 · answered May 02 '16 at 13:20

0

This should do the trick:

module Categorizable
  def after_save
    # Get the base class. Please note, this will work on 1 level deep STI
    klass = self.type.blank? ? self.class : self.class.superclass

    siblings = klass.where(category: self.category)

    # ...
  end
end

answered May 02 '16 at 13:20

Uzbekjon

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What if there are multiple subclasses? – hakunin May 02 '16 at 14:18
There can be multiple subclasses (`B – Uzbekjon May 02 '16 at 14:23
Thanks, I already have a solution that works for that case too. I will post it if no one comes up with a better one tomorrow. – hakunin May 02 '16 at 16:59

ActiveRecord single table inheritance - how to get root model?

2 Answers2