Rails 5 ApplicationRecord inheritance with exception

Question

I want all my models to inherit a validation present in my ApplicationRecord file except the user model. Is there a way to achieve that?
This is the line validates :user_id, presence: true

Answer 1

I wouldn't recommend putting that in ApplicationRecord since it's meant to be the parent of all modules, but if you really want to do it:

class ApplicationRecord < ActiveRecord::Base
  validates :user_id, presence: true, unless: 'self.class.to_s == "User"'
  ...
end

But i strongly suggest against it. This would make your code counter intuitive and future developers would have trouble understanding why it functions like that. Not to mention any future records you create, you explicitly have to set presence: false .