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Date: Sat, 23 Nov 2024 18:35:41 +0100 (CET)
To: Rob Landers <rob@bottled.codes>, internals@lists.php.net
Message-ID: <1438199905.177050.1732383341616@email.ionos.de>
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References: <18b85ba5-5f1c-489c-9096-3ae203977fbe@app.fastmail.com>
Subject: Re: [PHP-DEV] [RFC] Data Classes
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From: mails@thomasbley.de (Thomas Bley)

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=20

> Rob Landers <rob@bottled.codes> hat am 23.11.2024 14:11 CET geschrieben:
> =20
> =20
> Hello internals,
> =20
> Born from the Records RFC (https://wiki.php.net/rfc/records) discussion, =
I would like to introduce to you a competing RFC: Data Classes (https://wik=
i.php.net/rfc/dataclass).=20
> =20
> This adds a new class modifier: data. This modifier drastically changes h=
ow classes work, making them comparable by value instead of reference, and =
any mutations behave more like arrays than objects (by vale). If desired, i=
t can be combined with other modifiers, such as readonly, to enforce immuta=
bility.
> =20
> I've been playing with this feature for a few days now, and it is surpris=
ingly intuitive to use. There is a (mostly) working implementation availabl=
e on GitHub (https://github.com/php/php-src/pull/16904) if you want to have=
 a go at it.
> =20
> Example:
> =20
> data class UserId { public function __construct(public int $id) {} }
> =20
> $user =3D new UserId(12);
> // later
> $admin =3D new UserId(12);
> if ($admin =3D=3D=3D $user) { // do something } // true
> =20
> Data classes are true value objects, with full copy-on-write optimization=
s:
> =20
> data class Point {
>   public function __construct(public int $x, public int $y) {}
>   public function add(Point $other): Point {
>     // illustrating value semantics, no copy yet
>     $previous =3D $this;
>     // a copy happens on the next line
>     $this->x =3D $this->x + $other->x;
>     $this->y =3D $this->y + $other->y;
>     assert($this !=3D=3D $previous); // passes
>     return $this;
>   }
> }
> =20
> I think this would be an amazing addition to PHP.=20
> =20
> Sincerely,
> =20
> =E2=80=94 Rob
>=20
=20
Thanks for the rfc!
From userland perspective I would prefer to have the cloning more explicitl=
y, e.g.

return clone $this($this->x + $other->x, $this->y + $other->y);
=20
or
=20
return clone $this(x: $this->x + $other->x); // clone with y unchanged
=20
Best Regards
Thomas

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<!doctype html>
<html>
 <head>
  <meta charset=3D"UTF-8">
 </head>
 <body>
  <div>
   &nbsp;
  </div>
  <blockquote type=3D"cite">
   <div>
    Rob Landers &lt;rob@bottled.codes&gt; hat am 23.11.2024 14:11 CET gesch=
rieben:
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    Hello internals,
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    Born from the Records RFC (<a href=3D"https://wiki.php.net/rfc/records"=
>https://wiki.php.net/rfc/records</a>) discussion, I would like to introduc=
e to you a competing RFC: Data Classes (<a href=3D"https://wiki.php.net/rfc=
/dataclass">https://wiki.php.net/rfc/dataclass</a>).&nbsp;
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    This adds a new class modifier: data. This modifier drastically changes=
 how classes work, making them comparable by value instead of reference, an=
d any mutations behave more like arrays than objects (by vale). If desired,=
 it can be combined with other modifiers, such as readonly, to enforce immu=
tability.
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    I've been playing with this feature for a few days now, and it is surpr=
isingly intuitive to use. There is a (mostly) working implementation availa=
ble on GitHub (<a href=3D"https://github.com/php/php-src/pull/16904">https:=
//github.com/php/php-src/pull/16904</a>) if you want to have a go at it.
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    Example:
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    data class UserId { public function __construct(public int $id) {} }
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    $user =3D new UserId(12);
   </div>
   <div>
    // later
   </div>
   <div>
    $admin =3D new UserId(12);
   </div>
   <div>
    if ($admin =3D=3D=3D $user) { // do something } // true
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    Data classes are true value objects, with full copy-on-write optimizati=
ons:
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    data class Point {
   </div>
   <div>
    &nbsp; public function __construct(public int $x, public int $y) {}
   </div>
   <div>
    &nbsp; public function add(Point $other): Point {
   </div>
   <div>
    &nbsp; &nbsp; // illustrating value semantics, no copy yet
   </div>
   <div>
    &nbsp; &nbsp; $previous =3D $this;
   </div>
   <div>
    &nbsp; &nbsp; // a copy happens on the next line
   </div>
   <div>
    &nbsp; &nbsp; $this-&gt;x =3D $this-&gt;x + $other-&gt;x;
   </div>
   <div>
    &nbsp; &nbsp; $this-&gt;y =3D $this-&gt;y + $other-&gt;y;
   </div>
   <div>
    &nbsp; &nbsp; assert($this !=3D=3D $previous); // passes
   </div>
   <div>
    &nbsp; &nbsp; return $this;
   </div>
   <div>
    &nbsp; }
   </div>
   <div>
    }
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    I think this would be an amazing addition to PHP.&nbsp;
   </div>
   <div>
    &nbsp;
   </div>
   <div>
    Sincerely,
   </div>
   <div>
    &nbsp;
   </div>
   <div id=3D"sig121229152">
    =E2=80=94 Rob
   </div>
  </blockquote>
  <div>
   &nbsp;
  </div>
  <div class=3D"default-style">
   Thanks for the rfc!
  </div>
  <div class=3D"default-style">
   From userland perspective I would prefer to have the cloning more explic=
itly, e.g.
   <br>
   <br>
   return clone $this($this-&gt;x + $other-&gt;x, $this-&gt;y + $other-&gt;=
y);
  </div>
  <div class=3D"default-style">
   &nbsp;
  </div>
  <div class=3D"default-style">
   or
  </div>
  <div class=3D"default-style">
   &nbsp;
  </div>
  <div class=3D"default-style">
   return clone $this(x: $this-&gt;x + $other-&gt;x); // clone with y uncha=
nged
  </div>
  <div class=3D"default-style">
   &nbsp;
  </div>
  <div class=3D"default-style">
   Best Regards
  </div>
  <div class=3D"default-style">
   Thomas
  </div>
 </body>
</html>
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