Newsgroups: php.internals Path: news.php.net Xref: news.php.net php.internals:95747 Return-Path: Mailing-List: contact internals-help@lists.php.net; run by ezmlm Delivered-To: mailing list internals@lists.php.net Received: (qmail 45946 invoked from network); 7 Sep 2016 12:53:48 -0000 Received: from unknown (HELO lists.php.net) (127.0.0.1) by localhost with SMTP; 7 Sep 2016 12:53:48 -0000 Authentication-Results: pb1.pair.com smtp.mail=mathieu@rochette.cc; spf=pass; sender-id=pass Authentication-Results: pb1.pair.com header.from=mathieu@rochette.cc; sender-id=pass Received-SPF: pass (pb1.pair.com: domain rochette.cc designates 62.210.206.189 as permitted sender) X-PHP-List-Original-Sender: mathieu@rochette.cc X-Host-Fingerprint: 62.210.206.189 texthtml.net Received: from [62.210.206.189] ([62.210.206.189:57949] helo=texthtml.net) by pb1.pair.com (ecelerity 2.1.1.9-wez r(12769M)) with ESMTP id 07/50-43559-BDD00D75 for ; Wed, 07 Sep 2016 08:53:48 -0400 Received: by texthtml.net (Postfix, from userid 65534) id 0A438232; Wed, 7 Sep 2016 12:53:44 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on a05d8528c5e6 X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,HTML_MESSAGE autolearn=unavailable autolearn_force=no version=3.4.1 Received: from [192.168.1.130] (stunnel_mail_1.mail_default [172.29.0.4]) (Authenticated sender: mathieu@texthtml.net) by texthtml.net (Postfix) with ESMTPA id 1B24B29C; Wed, 7 Sep 2016 12:53:29 +0000 (UTC) To: =?UTF-8?Q?Micha=c5=82_Brzuchalski?= , PHP Internals List 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> Message-ID: Date: Wed, 7 Sep 2016 14:53:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:50.0) Gecko/20100101 Thunderbird/50.0a2 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/alternative; boundary="------------917015D69663FDB5E0BC28AC" Content-Language: en-US Subject: Re: [PHP-DEV] RFC - Immutable classes From: mathieu@rochette.cc (Mathieu Rochette) --------------917015D69663FDB5E0BC28AC Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit 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 end of the block/method better, here are 2 examples to illustrate what I mean class immutable foo { private $prop = 0; public function __construct($v) {$this->prop = $v;} public function bar(obj $o) { $e->makeSomethingWith($this->cloneAndEdit(42)); } public function many($n) { $a = []; for ($i = 0; $i < $n; $i++) { $a[] = $this->cloneAndEdit($i)); } return $a; } public function mut cloneAndEdit($n) { $clone->prop = $n; } } // vs class immutable foo { private $prop = 0; public function __construct($v) {$this->prop = $v;} public function bar(obj $o) { $c = $clone $this; $c->prop = 42; $e->makeSomethingWith($c); } public function many($n) { $a = []; for ($i = 0; $i < $n; $i++) { $a[] = $c = $clone $this; $c->prop = 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, Michał 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 environments. >> >> 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 = $y with ($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 = $value; >> } >> >> } >> >> > Providing `mutator` | `mut` keyword as method modifier sounds liek a good > idea, > althought passing `$clone` parameter as first additional param could break > 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` but > not `$this` > but I don't see the need of it - assuming there is no what to change in some > circumstances ther would be also possible to return `$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 = new ValueObject(1); >> $vo2 = $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 >> >> > --------------917015D69663FDB5E0BC28AC--