updating attributes with accepts_nested_attributes_for

I have two models User and Advert. User has_many :adverts and Advert belongs_to :user. I use accepts_nested_attributes_for to update adverts attributes. This is how I do it:

class Users::RegistrationsController < Devise::RegistrationsController 
   @user = current_user 
   @user.update_attributes(adverts_attributes: [{id: ???, show_advert: false}])
end

For @user to be able to update advert he needs to have advert ID. If I just type ID advert e.g. 112 this works fine. I have also tried this way:

Advert.all.each do |advert|
  @advert = advert.id
end

Worked only for oldest advert.

So how can I access advert ID?