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The WeakMap class

(PECL weakref >= 0.2.0)

Introducere

Sinopsisul clasei

WeakMap implements Countable , ArrayAccess , Iterator {

/* Metode */

public __construct ( )

public count ( ) : int

public current ( ) : mixed

public key ( ) : object

public next ( ) : void

public offsetExists ( object $object ) : bool

public offsetGet ( object $object ) : mixed

public offsetSet ( object $object , mixed $value ) : void

public offsetUnset ( object $object ) : void

public rewind ( ) : void

public valid ( ) : bool

}

Exemple

Example #1 Weakmap usage example


<?php
$wm = new WeakMap();

$o = new StdClass;

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

$wm[$o] = new A;

var_dump(count($wm));
echo "Unsetting...\n";
unset($o);
echo "Done\n";
var_dump(count($wm));

Exemplul de mai sus va afișa:

int(1)
Unsetting...
Dead!
Done
int(0)

Cuprins

WeakMap::__construct — Constructs a new map
WeakMap::count — Counts the number of live entries in the map
WeakMap::current — Returns the current value under iteration
WeakMap::key — Returns the current key under iteration
WeakMap::next — Advances to the next map element
WeakMap::offsetExists — Checks whether a certain object is in the map
WeakMap::offsetGet — Returns the value pointed to by a certain object
WeakMap::offsetSet — Updates the map with a new key-value pair
WeakMap::offsetUnset — Removes an entry from the map
WeakMap::rewind — Rewinds the iterator to the beginning of the map
WeakMap::valid — Returns whether the iterator is still on a valid map element

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User Contributed Notes 1 note

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Samu ¶

1 year 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.

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