active_record_building.md

При инициализации объекта ApplicationRecord с существующим id, все связанные ассоциаций начинают удаляться из БД при их назначении

class Order < ApplicationRecord
  has_one :order_payment, dependent: :delete
end

class OrderPayment < ApplicationRecord
  belongs_to :order
end

> order = Order.create!
=> #<Order id: 1>

> OrderPayment.create! order_id: order.id
=> #<OrderPayment id: 1, order_id: 1>

> Order.new(id: 1, order_payment: OrderPayment.new)

OrderPayment Load (4.8ms)  SELECT  "order_payments".* FROM "order_payments" WHERE "order_payments"."order_id" = ? LIMIT ?  [["order_id", 1], ["LIMIT", 1]]
OrderPayment Destroy (13.8ms)  DELETE FROM "order_payments" WHERE "order_payments"."id" = ?  [["id", 1]]

Rails 5.2.3, ruby 2.6.4

klondaiker/active_record_building.md