Newsgroups: php.internals Path: news.php.net Xref: news.php.net php.internals:95748 Return-Path: Mailing-List: contact internals-help@lists.php.net; run by ezmlm Delivered-To: mailing list internals@lists.php.net Received: (qmail 50139 invoked from network); 7 Sep 2016 13:09:28 -0000 Received: from unknown (HELO lists.php.net) (127.0.0.1) by localhost with SMTP; 7 Sep 2016 13:09:28 -0000 Authentication-Results: pb1.pair.com header.from=michal@brzuchalski.com; sender-id=pass Authentication-Results: pb1.pair.com smtp.mail=michal@brzuchalski.com; spf=pass; sender-id=pass Received-SPF: pass (pb1.pair.com: domain brzuchalski.com designates 188.165.245.118 as permitted sender) X-PHP-List-Original-Sender: michal@brzuchalski.com X-Host-Fingerprint: 188.165.245.118 ns220893.ip-188-165-245.eu Received: from [188.165.245.118] ([188.165.245.118:41227] helo=poczta.brzuchalski.com) by pb1.pair.com (ecelerity 2.1.1.9-wez r(12769M)) with ESMTP id 1B/B0-43559-58110D75 for ; Wed, 07 Sep 2016 09:09:27 -0400 Received: from localhost (localhost.localdomain [127.0.0.1]) by poczta.brzuchalski.com (Postfix) with ESMTP id 0707B2984246 for ; Wed, 7 Sep 2016 15:09:23 +0200 (CEST) Received: from poczta.brzuchalski.com ([127.0.0.1]) by localhost (poczta.brzuchalski.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id L7xlLkqFD1Lc for ; Wed, 7 Sep 2016 15:09:19 +0200 (CEST) Received: from mail-qt0-f182.google.com (unknown [209.85.216.182]) by poczta.brzuchalski.com (Postfix) with ESMTPSA id A42EE2984245 for ; Wed, 7 Sep 2016 15:09:18 +0200 (CEST) Received: by mail-qt0-f182.google.com with SMTP id p30so6826685qte.3 for ; Wed, 07 Sep 2016 06:09:18 -0700 (PDT) X-Gm-Message-State: AE9vXwPZFXN2sebxXajN5MuSswkMdvJpUBbaaZTCOkBoRDYhVoLgL6xd6zm8a/9ksz73TpqSqQG3cflThgCGCA== X-Received: by 10.237.46.6 with SMTP id j6mr51615790qtd.113.1473253757798; Wed, 07 Sep 2016 06:09:17 -0700 (PDT) MIME-Version: 1.0 Received: by 10.200.56.100 with HTTP; Wed, 7 Sep 2016 06:09:16 -0700 (PDT) In-Reply-To: References: <99F80C06-654D-4109-BE07-2FA5B1073E5D@ez.no> <4f54308a-4a69-2e6b-2ed0-51d4336d1cd4@fleshgrinder.com> <5969d1af-48e5-1376-07fe-9568de538145@texthtml.net> <0e71d28e-1d64-5372-b58d-e54c7afae3b8@fleshgrinder.com> Date: Wed, 7 Sep 2016 15:09:16 +0200 X-Gmail-Original-Message-ID: Message-ID: To: Mathieu Rochette Cc: PHP Internals List Content-Type: multipart/alternative; boundary=94eb2c124000e5dc1c053bea9ecb Subject: Re: [PHP-DEV] RFC - Immutable classes From: michal@brzuchalski.com (=?UTF-8?Q?Micha=C5=82_Brzuchalski?=) --94eb2c124000e5dc1c053bea9ecb Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable @Mathieu How about that: https://gist.github.com/brzuchal/e7b721e22a19cca42ec0d1f597a23baf We've discussed this could be best option, when invoking `transformer` method (or whatever we call it) there is `$this =3D clone $this` invoked under the hood. 2016-09-07 14:53 GMT+02:00 Mathieu Rochette : > a few remarks on mutator methods: > > - It could be a nice way to solve the "create another one almost the > same" use case. > - I don't mind if $clone is an explicit parameter or magically > available > - what happens if I call other function/methods with this $clone > before the end of the function ? > - and the only downside: I have to make a method just for cloning. > that means I have to call a mutator multiple times if I want to make a > bunch of clone, eg: > > because of the last point, I think I'd like the seal the clone at then en= d > of the block/method better, here are 2 examples to illustrate what I mean > class immutable foo { > private $prop =3D 0; > > public function __construct($v) {$this->prop =3D $v;} > > public function bar(obj $o) { > $e->makeSomethingWith($this->cloneAndEdit(42)); > } > > public function many($n) { > $a =3D []; > for ($i =3D 0; $i < $n; $i++) { > $a[] =3D $this->cloneAndEdit($i)); > } > return $a; > > } > > public function mut cloneAndEdit($n) { > $clone->prop =3D $n; > } > } > > // vs > > class immutable foo { > private $prop =3D 0; > > public function __construct($v) {$this->prop =3D $v;} > > public function bar(obj $o) { > $c =3D $clone $this; > $c->prop =3D 42; > $e->makeSomethingWith($c); > } > > public function many($n) { > $a =3D []; > for ($i =3D 0; $i < $n; $i++) { > $a[] =3D $c =3D $clone $this; > $c->prop =3D 42; > } > return $a; > } > } > > I understand that it's still not clear exactly when the object should be > sealed but if it can works this one would have my preference > On 04/09/2016 14:10, Micha=C5=82 Brzuchalski wrote: > > 2016-09-04 10:55 GMT+02:00 Fleshgrinder : > > > Hi Chris! > > On 9/3/2016 5:00 PM, Chris Riley wrote: > > - Properties can be declared immutable. Immutable properties may only be > changed under two circumstances: a) In the objects constructor b) If they > are null (This enables setter injection if required) > > > The constraint b) would make the object mutable and defeat the purpose > of the immutable modifier since any property could change at any time if > it was NULL at the beginning. Requiring syncing in concurrent environment= s. > > On 9/3/2016 5:00 PM, Chris Riley wrote: > > - Arrays assigned to immutable properties would not be possible to change > > > Array support would definitely be very nice. I mean, we have constant > arrays already, hence, it is possible. > > On 9/3/2016 5:00 PM, Chris Riley wrote: > > - Objects assigned to immutable properties would be possible to change, > > so > > long as the same object remained assigned to the property. > > > This would once more lead to mutability and the constraint of > immutability would be violated. > > On 9/3/2016 5:00 PM, Chris Riley wrote: > > From a developer adoption point of view, I think these two points are > important to making immutable classes generally useful. Without 1, it > > will > > be a nuisance to use 3rd party libraries esp those which retain > compatibility for PHP < 7.2. Without 2 you block the ability to use > > setter > > injection, which I personally would be in favour of if it meant that devs > stopped using it - it wouldn't - they would simply not use immutable > classes, loosing the benefits thereof. > > > The adoption of the feature will be halted until 7.2 is widely available > in bigger projects. That is most certainly right. However, we should aim > for the best, most useful, and future proof solution and not towards the > one that's adopted very fast but lacks some important constraints. > Having truly immutable objects is required in concurrent scenarios and > such scenarios are in the future for PHP and not in the past. > > Regarding setter injection: I do not see the need for it at all in the > context of immutable objects. In the end we are talking about value > objects here and they should not have any optional dependencies. Maybe > you could come up with a use case to illustrate the need? > > On 9/3/2016 5:00 PM, Chris Riley wrote: > > Dealing with the clone issue some of my ideas since then were: > > - Seal/Unseal (As per Larry's suggestion) > - Parameters to __clone; in this instance the clone method would be > > allowed > > to change properties of the object as well as the constructor. This feels > like it may breach the principal of least surprise as cloning an object > > no > > longer guarantees an exact copy. > - A new magic method __mutate($property, $newvalue) called instead of a > fatal error when a property is changed. This probably lays too many traps > for developers for it to be a good idea. > - Implicitly returning a new object whenever a property is changed. > > Similar > > reservations to the above. > - A new magic method __with($newInstance, $args) and a keyword with that > > is > > used in place of clone eg $x =3D $y with ($arg1, $arg2); in this instance= , > __with receives a clone of $y (after calling __clone) and an array > > [$arg1, > > $arg2] the with magic method is allowed to mutate $newInstance and must > return it. This is currently my favoured solution > > > How does one know which property is to be mutated in the __with method? > You should also not underestimate the performance hit and the branching > since you only want to change the properties that changed based on the > data from the passed array. > > I have a third proposal after giving this some more thought. Inspired by > Rust's approach to mark mutation explicitly. > > final immutable class ValueObject { > > public $value; > > public mutator [function] withValue($clone, $value): static { > $clone->value =3D $value; > } > > } > > > > Providing `mutator` | `mut` keyword as method modifier sounds liek a good > idea, > althought passing `$clone` parameter as first additional param could brea= k > method declaration and would be misleading. > > Assuming mutator method is designed to return mutated clone of immutable > object > having `$clone` variable could be handled internally without breaking > method declaration. > > Such variable could be unlocked while in mutator method and locked on > return. > I was thinking about additional check if such mutator returns `$clone` bu= t > not `$this` > but I don't see the need of it - assuming there is no what to change in s= ome > circumstances ther would be also possible to return `$this`. > > The return type declaration `self` could increase readability, but should > not be required, > as some developers doesn't already use return types. > > > > A mutator function always receives the mutable clone as first argument > and always returns that one. Users can have a return but they must > return the clone (hence the static return type declaration). > > $vo1 =3D new ValueObject(1); > $vo2 =3D $vo1->withValue(2); > > Calls are of course without the clone as it is handled by the engine. > There is no special branching necessary and no performance hit at all > while the logic is kept in the place where it is required. > > -- > Richard "Fleshgrinder" Fussenegger > > > > > --=20 regards / pozdrawiam, -- Micha=C5=82 Brzuchalski brzuchalski.com --94eb2c124000e5dc1c053bea9ecb--