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Date: Sat, 11 Jul 2020 16:25:50 -0500
To: "php internals" <internals@lists.php.net>
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Subject: =?UTF-8?Q?Re:_[PHP-DEV]_Possible_RFC:_UniqueInterface_that_throws_except?=
 =?UTF-8?Q?ion_at_refcount_>_1?=
From: larry@garfieldtech.com ("Larry Garfield")

On Sat, Jul 11, 2020, at 4:04 PM, Olle H=C3=A4rstedt wrote:

> > I think that would do a far better job of addressing the
> > shared-mutable-state issue than reference counting, because it attac=
ks the
> > root problem rather than a symptom.
> >
> > --Larry Garfield
> >
> > --
> > PHP Internals - PHP Runtime Development Mailing List
> > To unsubscribe, visit: https://www.php.net/unsub.php
>=20
> I think freezing objects might be better fit for my imagined use-case.=

> The only problem I see is that you can't really unfreeze them. Imagine=

> a database connection that only can be open/closed at refcount =3D 1:
>=20
> ```
> $connection =3D new OwnershipConnection();
> $connection->open();
> $ps =3D new PostService($connection);
> $ps->updateAllPosts();  // Throws exception if $connection->close()
> $connection->close();
> ```
>=20
> With freeze, you could also do
>=20
> ```
> $ps =3D new PostService($connection->freeze());
> ```
>=20
> to ensure it's not closed by mistake. But then you couldn't close the
> connection at all, except in __destruct.
>=20
> Especially, CoW for objects (at opt-in) is not a replacement where
> ownership is supposed to replace immutability for performance reason,
> e.g. creating a separate immutable database connection for every class=

> that uses it.
>=20
> Immutable builder are already part of PSR, e.g. here:
> https://www.php-fig.org/psr/psr-7/
>=20
> I have to wonder how reasonable this is, when freezing or ownership
> are also relevant solutions, with different trade-offs.
>=20
> Olle

A database connection is the textbook example of an object that *should*=
 be shared; giving a separate connection to every service object is only=
 going to waste time opening multiple connections and waste open connect=
ions.  Please don't do that.

Your example seems directly contrary to the goal you're describing.

--Larry Garfield