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 <A54E52AF-7345-4AED-8DF1-BFCB93C925CF@trowski.com>
In-Reply-To: <A54E52AF-7345-4AED-8DF1-BFCB93C925CF@trowski.com>
Date: Sat, 22 Jan 2022 18:57:43 +0000
Message-ID: <CAFKaYMonjSiWBomTQPX43=5B7+byp1GvbSQSx4wgRMpBxcV3oQ@mail.gmail.com>
To: Aaron Piotrowski <aaron@trowski.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Weak Closures
From: codekestrel@googlemail.com (Dominic Grostate)

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Yes while experimenting I found that solution to work. In order to support
$this->func(...) Though I had to use reflection to separate the object and
method name.

On Sat, 22 Jan 2022, 16:12 Aaron Piotrowski, <aaron@trowski.com> wrote:

>
> > On Jan 21, 2022, at 4:31 AM, Dominic Grostate <
> codekestrel@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
>
>

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