How do I 'validate' on destroy in rails
You can raise an exception which you then catch. Rails wraps deletes in a transaction, which helps matters.
For example:
class Booking < ActiveRecord::Base
has_many :booking_payments
....
def destroy
raise "Cannot delete booking with payments" unless booking_payments.count == 0
# ... ok, go ahead and destroy
super
end
end
Alternatively you can use the before_destroy callback. This callback is normally used to destroy dependent records, but you can throw an exception or add an error instead.
def before_destroy
return true if booking_payments.count == 0
errors.add :base, "Cannot delete booking with payments"
# or errors.add_to_base in Rails 2
false
# Rails 5
throw(:abort)
end
myBooking.destroy
will now return false, and myBooking.errors
will be populated on return.
just a note:
For rails 3
class Booking < ActiveRecord::Base
before_destroy :booking_with_payments?
private
def booking_with_payments?
errors.add(:base, "Cannot delete booking with payments") unless booking_payments.count == 0
errors.blank? #return false, to not destroy the element, otherwise, it will delete.
end