Why is destroying nested records happening on update_attributes and not on the parent save?

Question

I have two associated models:

class HelpRequest < ActiveRecord::Base
  has_many :donation_items, dependent: :destroy
  accepts_nested_attributes_for :donation_items, allow_destroy: true

and

class DonationItem < ActiveRecord::Base
  belongs_to :help_request

I have a validator that returns an error to the user if he/she tries to save a help_request with no donation_items.

validate :has_donation_items?
...
def has_donation_items?
  if !self.donation_items.present?
    errors.add :a_help_request, "must have at least one item."
  end
end

I'm updating both the help_request and the donation_items from within a nested form in which the user can destroy single or multiple donation_items. According to this, if the user destroys any donation_items they shouldn't get destroyed in the database until the parent is saved. But I've verified that in my case, they're being destroyed immediately upon running the update_attributes method. Here's stripped down code:

@help_request.update_attributes(help_request_params) # donation items get destroyed in the database right here
# do some stuff
if @help_request.save
  #do some other stuff if the save is successful

Here's the help_request_params with nested attributes:

def help_request_params
  params.require(:help_request).permit(:id, :name, :description, :event_flag, :due_on_event, :date, :time, :send_notification, :event_id, :invoked, donation_items_attributes: [:id, :name, :amount, :_destroy])
end

Is there a reason why the database seems to be getting updated on update_attributes?

Answer 1

Think I figured it out. update_attributes saves (or attempts to) immediately. Instead, I've switched to assign_attributes. Working out some other kinks, but it seems to have resolved the main problem.