ensure-record-saved-with-after-commit-callback.md

Ensure Record Saved With after_commit Callback

In my experience, some of the more common ActiveRecord callbacks are ones like before_save or after_update. While working with some code, where I needed to send a notification when a certain value was updated, I learned that something like after_update wasn't sufficient.

If my record is updated within a transaction, the after_update will get triggered even though the changes could later get rolled back resulting in me erroneously sending the notification.

ActiveRecord::Base.transaction do
  user.update(interesting_value: 123)

  do_something # <-- rollback could happen here!
end

To ensure I'm not over-eager with my notifications, I should instead use after_commit which only gets called after the changes have been committed to the database.

class User < ApplicationRecord
  after_commit :send_notification,
    on: [:create, :update],
    if: :interesting_value_was_changed?

  # rest of class...

  private

  def send_notification
    # logic...
  end

  def interesting_value_was_changed?
    # logic...
  end
end

On either create or update if my condition is met, then after the commit goes through, the #send_notification method will be triggered.