Rails conditional validation in model

Question

I have a Rails 3.2.18 app where I'm trying to do some conditional validation on a model.

In the call model there are two fields :location_id (which is an association to a list of pre-defined locations) and :location_other (which is a text field where someone could type in a string or in this case an address).

What I want to be able to do is use validations when creating a call to where either the :location_id or :location_other is validated to be present.

I've read through the Rails validations guide and am a little confused. Was hoping someone could shed some light on how to do this easily with a conditional.

I don't quite understand the core question. Is it about how to use the if and unless options of the valdates macros? Or is it about how to only validate on certain model attributes when saving a model from some controller actions (and not others)? — pdobb
– pdobb, Commented Jul 8, 2014 at 20:31
Sorry for the confusion. I'm trying to figure out how to use if and unless when creating/saving a record. The end goal is to verify that either the :location_id or :location_other is set when creating/saving a record. I'm just not sure how to do it. — nulltek
– nulltek, Commented Jul 8, 2014 at 20:38

Joe Kennedy · Accepted Answer · 2015-10-27 14:16:09Z

I believe this is what you're looking for:

class Call < ActiveRecord::Base
  validate :location_id_or_other

  def location_id_or_other
    if location_id.blank? && location_other.blank?
      errors.add(:location_other, 'needs to be present if location_id is not present')
    end
  end
end

location_id_or_other is a custom validation method that checks if location_id and location_other are blank. If they both are, then it adds a validation error. If the presence of location_id and location_other is an exclusive or, i.e. only one of the two can be present, not either, and not both, then you can make the following change to the if block in the method.

if location_id.blank? == location_other.blank?
  errors.add(:location_other, "must be present if location_id isn't, but can't be present if location_id is")
end

Alternate Solution

class Call < ActiveRecord::Base
  validates :location_id, presence: true, unless: :location_other
  validates :location_other, presence: true, unless: :location_id
end

This solution (only) works if the presence of location_id and location_other is an exclusive or.

Check out the Rails Validation Guide for more information.

Thank you for the quick response. The first solution, creating a custom validation did the trick. I was just doing some research on custom validations and started to write something similar, thanks for saving me time and teaching me. I appreciate it!
No problem! And check out the Rails Validation Guide (which I also linked in my updated answer) for more info about validations.
Thanks! That's what I've been reading and was going off of when I started writing something similar. But thanks again for stepping in so fast and coming up with a simple answer. Much appreciated.

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