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WeakMap sınıfı

(PHP 8)

Giriş

WeakMap nesneleri anahtar olarak kabul eden bir haritadır (veya sözlüktür). Ancak, SplObjectStorage'dan farklı olarak, WeakMap anahtarındaki nesne, nesnenin gönderim sayısına katkıda bulunmaz. Yani, herhangi bir noktada bir nesneye kalan tek gönderim bir WeakMap anahtarı ise, nesne çöp olarak toplanacak ve WeakMap'ten kaldırılacaktır. Birincil kullanım durumu, nesneden daha uzun yaşaması gerekmeyen bir nesneden türetilen verilerin arabelleklerini oluşturmak içindir.

WeakMap sınıfı ArrayAccess, Iterator ve Countable arayüzlerini gerçekler, bu yüzden çoğu durumda ilişkili bir dizi gibi kullanılabilir.

Sınıf Sözdizimi

final class WeakMap implements ArrayAccess, Countable, IteratorAggregate {
/* Yöntemler */
public count(): int
public offsetExists(object $nesne): bool
public offsetGet(object $nesne): mixed
public offsetSet(object $nesne, mixed $değer): void
public offsetUnset(object $girdi): void
}

Örnekler

Örnek 1 - Weakmap kullanım örneği

<?php
$wm
= new WeakMap();

$o = new stdClass;

class
A {
public function
__destruct() {
echo
"Öldü!\n";
}
}

$wm[$o] = new A;

var_dump(count($wm));
echo
"Yok ediliyor...\n";
unset(
$o);
echo
"İşi bitti\n";
var_dump(count($wm));

Yukarıdaki örneğin çıktısı:

int(1)
Yok ediliyor...
Öldü!
İşi bitti
int(0)

İçindekiler

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User Contributed Notes 2 notes

up
6
Samu
4 months ago
PHP's implementation of WeakMap allows for iterating over the contents of the weak map, hence it's important to understand why it is sometimes dangerous and requires careful thought.

If the objects of the WeakMap are "managed" by other services such as Doctrine's EntityManager, it is never safe to assume that if the object still exists in the weak map, it is still managed by Doctrine and therefore safe to consume.

Doctrine might have already thrown that entity away but some unrelated piece of code might still hold a reference to it, hence it still existing in the map as well.

If you are placing managed objects into the WeakMap and later iterating over the WeakMap (e.g. after Doctrine flush), then for each such object you must verify that it is still valid in the context of the source of the object.

For example assigning a detached Doctrine entity to another entity's property would result in errors about non-persisted / non-managed entities being found in the hierarchy.
up
0
Anton
10 days ago
Keep in mind that if Enum case is put as a key to WeakMap, it will never be removed because it will always have unless 1 reference to it under the hood (not sure why, probably because enum is basically a constant).
Therefore, both WeakMaps below will always have key Enum::Case. However, you still are able to unset it manually:

$weakMap = new WeakMap();
$object = Enum::Case;

$weakMap[$object] = 123;
unset($object);
var_dump($weakMap->count()); // 1

///

$weakMap = new WeakMap();
$weakMap[Enum::Case] = 123;
var_dump($weakMap->count()); // 1

///

$weakMap = new WeakMap();
$weakMap[Enum::Case] = 123;
unset($weakMap[Enum::Case]);
var_dump($weakMap->count()); // 0
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