How can I skip active record validations in some special cases?

Question

I have a Ruby on Rails application for human resource planning. Normally, it is not allowed to delete entries from the past. From time to time, however, I have to delete users and, of course, I want to delete all entries from these users.

My user model:

has_many :team_memberships, dependent: :destroy
has_many :slots, through: :team_memberships, source: :slot

TeamMembership model:

before_destroy :check_permission
def check_permission
  if self.slot.start_time < Time.now.beginning_of_day
    errors.add(:base, "Historische Einträge können nicht gelöscht werden")
    return false
   end
end

I have a rake task that should destroy old users, but that doesn't work when they have historical entries because the validation fails.

How can I skip the before_destroy validation when User.destroy is called via a rake task? Any ideas?

Answer 1

You could add a new method to your model that set a variable and use that as a return value of the callback:

before_destroy :check_permission

def allow_deletion!
  @allow_deletion = true
end

def check_permission
  if !@allow_deletion && self.slot.start_time < Time.now.beginning_of_day
    errors.add(:base, "Historische Einträge können nicht gelöscht werden")
    return false
  end
end

That allows you to write something like this:

user.allow_deletion!
user.destroy

This method has the benefit over delete that you only skip this specific callback and not all callbacks and dependent destroy operations.