> On Jan 21, 2022, at 4:31 AM, Dominic Grostate <codekest...@googlemail.com> > wrote: > > Hi Internals, > > I'd like to express my interest in a possible feature concerning weak > references. Currently closures created within a class appear to > contain a reference to the object that created it. This is of course > necessary in order for the closure to retain the necessary scope. > However I would like to suggest we have the option for closure to > weakly reference this object so that when the object is garbage > collected, the closure too may be rendered null or invalid > (inspectable). > > Consider the following example: > https://gist.github.com/orolyn/7651e4127759aad1736547490baa1394 > > The idea here is that without unset($sample) the loop would run > forever, because there is a reference to the callback from the object, > and in turn there is a reference to the object from the main stack. > With the unset($sample), the idea is that before the callback is even > called, the reference to the object is destroyed thusly so is the > reference to callback, and since the callback is only referenced now > in a WeakMap, the callback will finally be gone. > > In reality it appears there is a circular reference between the object > and the callback. I don't know if this is a bug or not, because from > what I can find PHP was fixed a long time ago to resolve circular > references. > > However if this is intentional, I would like the option to make the > closure weak for example: > > $c = WeakClosure::fromCallable(function () {}); > $c = Closure::fromCallable(function () {}, true); > > Please let me know your thoughts, because maybe there is a way of > achieving this with PHP as is. > > Kind regards, > Dominic > > -- > PHP Internals - PHP Runtime Development Mailing List > To unsubscribe, visit: https://www.php.net/unsub.php >
Hi Dominic, Implementing a weak closure is possible in user code. We've done so in Amp v3: https://github.com/amphp/amp/blob/379177aba93518e2df6d626677cbbdc48cc0d8ae/src/functions.php#L119-L171 I would be in favor of having this functionality available directly in PHP. Amp often uses references to object properties in static closures to avoid circular references to $this. There are other ways to accomplish this, such as a ref object like https://github.com/azjezz/psl/blob/21bf0cd3d6d6055fc88541e9b24f3140bd179b2d/src/Psl/Ref.php, but a weak-ref to $this would certainly be more convenient. Cheers, Aaron Piotrowski -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: https://www.php.net/unsub.php
