Active Record Callbacks là gì? Liệt kê các callback quan trọng.

before_validation → after_validation
→ before_save → before_create
→ (INSERT INTO DB)
→ after_create → after_save → after_commit

class Order < ApplicationRecord
  before_create  :generate_reference_code
  after_commit   :send_confirmation_email, on: :create

  private

  def generate_reference_code
    self.ref = SecureRandom.hex(6)
  end
end