验证多态关联的唯一性

Question

I'm trying to implement a validation for a polymorphic association, where I only want it to trigger on a certain type. Which is user.

I'd want something like this:

validates :room_id, uniqueness: { scope: tokenable_id if tokenable type is User }

how do I go about doing this. The other type is Customer. Which I want to allow the opportunity to be several.

Answer 1

I think you can use Conditional Validation

Sometimes it will make sense to validate an object only when a given predicate is satisfied. You can do that by using the :if and :unless options, which can take a symbol, a string, a Proc or an Array. You may use the :if option when you want to specify when the validation should happen. If you want to specify when the validation should not happen, then you may use the :unless option.

5.1 Using a Symbol with :if and :unless

You can associate the :if and :unless options with a symbol corresponding to the name of a method that will get called right before validation happens. This is the most commonly used option.

class Order < ActiveRecord::Base
  validates :room_id, uniqueness: { scope: :tokenable_id }, if: :is_right_type?

  # or maybe this will work
  validates :room_id, uniqueness: { scope: :tokenable_id }, if: :user?

  def is_right_type?
    type == "user"
  end
end