What is the best way to create a singleton entity in Symfony 4? - symfony

Question

I want to create a settings page, which only has a form in it. If the form is submitted it only updates settings entity but never creates another one. Currently, I achieved this like:
/**
* #param SettingsRepository $settingsRepository
* #return Settings
*/
public function getEntity(SettingsRepository $settingsRepository): Settings
{
$settings = $settingsRepository->find(1);
if($settings == null)
{
$settings = new Settings();
}
return $settings;
}
In SettingsController I call getEntity() method which returns new Settings entity (if the setting were not set yet) or already existing Settings entity (if setting were set at least once).
However my solution is quite ugly and it has hardcoded entity id "1", so I'm looking for a better solution.
Settings controller:
public function index(
Request $request,
SettingsRepository $settingsRepository,
FlashBagInterface $flashBag,
TranslatorInterface $translator,
SettingsService $settingsService
): Response
{
// getEntity() method above
$settings = $settingsService->getEntity($settingsRepository);
$settingsForm = $this->createForm(SettingsType::class, $settings);
$settingsForm->handleRequest($request);
if ($settingsForm->isSubmitted() && $settingsForm->isValid()) {
$em = $this->getDoctrine()->getManager();
$em->persist($settings);
$em->flush();
return $this->redirectToRoute('app_admin_settings_index');
}
return $this->render(
'admin/settings/index.html.twig',
[
'settings_form' => $settingsForm->createView(),
]
);
}

Answer 1

You could use Doctrine Embeddables here.
Settings, strictly speaking, should not be mapped to entities, since they are not identifiable, nor meant to be. That is, of course, a matter of debate. Really, a Settings object is more of a value object than an entity. Read here for more info.
So, in cases like these better than having a one to one relationship and all that fuzz, you probably will be fine with a simple Value Object called settings, that will be mapped to the database as a Doctrine Embeddable.
You can make this object a singleton by creating instances of it only in factory methods, making the constructor private, preventing cloning and all that. Usually, it is enough only making it immutable, meaning, no behavior can alter it's state. If you need to mutate it, then the method responsible for that should create a new instance of it.
You can have a a method like this Settings::createFromArray() and antoher called Settings::createDefaults() that you will use when you new up an entity: always default config.
Then, the setSettings method on your entity receieves only a settings object as an argument.
If you don't like inmutablity, you can also make setter methods for the Settings object.