2020-07-11 14:55 GMT, tyson andre <tysonandre...@hotmail.com>:
>> Yes, it would be a dynamic uniqueness system, kind of.
>>
>> Another more flexible alternative would be to add magic methods at
>> refcount = 1 and refcount > 1, possibly __owned() and __shared(int
>> $refcount), for classes that implement a TrackReferencesInterface or
>> similar. But this would need to do ~0 performance hit if not used,
>> don't know if possible.
>
> Then again, php already calls __destruct if it exists when the refcount goes
> to 0,
> so I may be overestimating the potential performance impact.
>
> There's a lot of edge cases - probably way more than I mention here.
> Running into those edge cases, you might find the feature unsatisfactory if
> it were to be implemented.
>
> For example,
> - The UniqueReferenceException itself creates a trace, that increments
> reference counts, which might itself cause a UniqueReferenceException.
> Workarounds for that would probably involve allowing multiple objects to
> reference a UniqueInterface, and then it would be a weaker guarantee.
> - unserialize() keeps extra references to ensure that it can delete the
> created objects if the original references were overwritten. __wakeup() and
> __unserialize()
> - The reference count is incremented when calling __destruct(), I think.
>
> ```
> <?php
> class UniqueObject implements UniqueInterface{
> public function __construct() {
> debug_zval_dump($this); // refcount 3 - and then what about
> `$GLOBALS['something'] = $this` inside __construct
> }
> public function someUtilMethod() {
> // object(UniqueObject)#1 (0) refcount(2){
> // }
> debug_zval_dump($this);
> }
> }
> // The reference count goes to 2 in someUtilMethod because there's 2
> references.
> // the temporary and $this.
> (new UniqueObject())->someUtilMethod();
> ```
>
> - Tyson
All good points. It's better to have a magic method that catches
changes in the refcount instead, just like __destruct but on any
change, not only at zero.
Olle
--
PHP Internals - PHP Runtime Development Mailing List
To unsubscribe, visit: https://www.php.net/unsub.php
