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 associatio

Answer 1

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.