Generate Uuid manually in constructor or via UuidGenerator annotation

问题

I am switching to Ramsey\Uuid and don't know what is the intended way to generate the Uuids.

Either as shown in the examples with an anntoation:

/**
 * @var UuidInterface
 *
 * @ORM\Id
 * @ORM\Column(type="uuid", unique=true)
 * @ORM\GeneratedValue(strategy="CUSTOM")
 * @ORM\CustomIdGenerator(class="Ramsey\Uuid\Doctrine\UuidGenerator")
 */
private $id;


public function __construct() {
}

Or manually in the constructor:

/**
 * @var UuidInterface
 *
 * @ORM\Id
 * @ORM\Column(type="uuid", unique=true)
 */
private $id;


public function __construct() {
    $this->id = Uuid::uuid4();
}

In the second case, I do not understand how an existing id would be set during hydration. I added a public setter for testing purposes, but it is not called! In my understanding, when loading from db, a new object is created, which executes the constructor and hence sets a new uuid. Then somehow, this uuid must be replaced by the one from the db record. Am I missing something?

However the big advantage that the id is available immediately is gone when using the annotation, since the generation only takes place when calling $em->persist(...).

There are also variants out there where the constructor takes an optional uuid argument and uses it if not null.

来源：https://stackoverflow.com/questions/53045546/generate-uuid-manually-in-constructor-or-via-uuidgenerator-annotation