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Date: Mon, 27 May 2024 07:13:33 +0300
Message-ID: <CAPyeZ4M02SKfsacTNC7SPAptRfLnPyYbOJMuAM9og-azbA0CxQ@mail.gmail.com>
Subject: [PHP-DEV] Extract ArrayAccessRead from ArrayAccess
To: php internals <internals@lists.php.net>
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From: udaltsov.valentin@gmail.com (Valentin Udaltsov)

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Hello, internals!

Recently I was implementing some collections and realized that I cannot use
`ArrayAccess` for immutable collections without throwing
`BadMethodCallException` in `offsetSet` and `offsetUnset`. I also cannot
have an `interface ReadonlyCollection extends ArrayAccess`, because
`offsetSet` and `offsetUnset` are mutators and have `TValue` in a
contravariant position.

Here's the idea: let's extract `ArrayAccess::offsetExists` and
`ArrayAccess::offsetGet` methods into a separate `ArrayAccessRead`
interface (name can be different) and allow read operations `$exists =
isset($object['key'])` and `$value = $object['key']` for objects of classes
that implement this interface. `ArrayAccess` will then extend
`ArrayAccessRead` and add the remaining 2 methods. Looks like this change
should not break backward compatibility.

```
interface ArrayAccessRead
{
    public function offsetExists(mixed $offset): bool;
    public function offsetGet(mixed $offset): mixed;
}

interface ArrayAccess extends ArrayAccessRead
{
    public function offsetSet(mixed $offset, mixed $value): void;
    public function offsetUnset(mixed $offset): void;
}

// then interfaces of the doctrine/collections package might look like this:

namespace Doctrine\Common\Collections;

interface ReadableCollection extends Countable, IteratorAggregate,
ArrayAccessRead {}
interface Collection extends ReadableCollection, ArrayAccess {}
```
-- 
Regards, Valentin Udaltsov

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<div dir=3D"ltr">Hello, internals!<br><br>Recently I was implementing some =
collections and realized that I cannot use `ArrayAccess` for immutable coll=
ections without throwing `BadMethodCallException` in `offsetSet` and `offse=
tUnset`. I also cannot have an `interface ReadonlyCollection extends ArrayA=
ccess`, because `offsetSet` and `offsetUnset` are mutators and have `TValue=
` in a contravariant position.<div><br></div><div>Here&#39;s the idea: let&=
#39;s extract `ArrayAccess::offsetExists` and `ArrayAccess::offsetGet` meth=
ods into a separate `ArrayAccessRead` interface (name can be different) and=
 allow read operations `$exists =3D isset($object[&#39;key&#39;])` and `$va=
lue =3D $object[&#39;key&#39;]` for objects of classes that implement this =
interface. `ArrayAccess` will then extend `ArrayAccessRead` and add the rem=
aining 2 methods. Looks like this change should not break backward compatib=
ility.</div><div><br>```</div><div>interface ArrayAccessRead<br>{<br>=C2=A0=
 =C2=A0 public function offsetExists(mixed $offset): bool;<br>=C2=A0 =C2=A0=
 public function offsetGet(mixed $offset): mixed;<br>}<br><br>interface Arr=
ayAccess extends ArrayAccessRead<br>{<br>=C2=A0 =C2=A0 public function offs=
etSet(mixed $offset, mixed $value): void;<br>=C2=A0 =C2=A0 public function =
offsetUnset(mixed $offset): void;<br>}</div><div><br></div><div>// then int=
erfaces of the=C2=A0doctrine/collections package might look like this:</div=
><div><br></div><div>namespace Doctrine\Common\Collections;<br></div><div><=
br></div><div>interface ReadableCollection extends Countable, IteratorAggre=
gate, ArrayAccessRead {}</div><div>interface Collection extends ReadableCol=
lection, ArrayAccess {}<br></div><div>```<br><span class=3D"gmail_signature=
_prefix">-- </span><br><div dir=3D"ltr" class=3D"gmail_signature" data-smar=
tmail=3D"gmail_signature"><div dir=3D"ltr">Regards, Valentin Udaltsov<br></=
div></div></div></div>

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