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Date: Thu, 26 Aug 2021 22:20:35 +0200
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To: Rowan Tommins <rowan.collins@gmail.com>
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Subject: Re: [PHP-DEV] Alternatives for encapsulation when using composition
 instead of inheritance
From: olleharstedt@gmail.com (=?UTF-8?Q?Olle_H=C3=A4rstedt?=)

2021-08-26 20:30 GMT+02:00, Rowan Tommins <rowan.collins@gmail.com>:
> On 26/08/2021 14:47, Olle H=C3=A4rstedt wrote:
>> Don't know if this already exists, but maybe we could consider
>> brainstorming or gather alternatives for different types of
>> encapsulation when using composition?
>
>
> Although not quite equivalent to your suggestions, these threads on
> making delegation to an encapsulated object might be interesting to you:
>
> *  https://externals.io/message/103353
> * https://github.com/php/php-src/pull/5168

Right, there are indeed a bunch of attempts and suggestions, some
downvoted, others abandoned.

I'm thinking adding namespaces to runtime might be a logical first
step. That would allow attributes to add logic like internal
properties for a certain namespace. Makes me wonder why that never
happened for this PR: https://github.com/php/php-src/pull/947

Asking anyone on the list, would it be possible to make an opcode out
of "namespace Foo\Bar" and letting it set a flag in the runtime system
when run? Then make the flag accessible with a constant like
__NAMESPACE_RUNTIME__ or whatever.

Ooooh, there's an interesting case with "goto" and namespace
visibility here:
https://github.com/php/php-src/pull/947#issuecomment-419821198

That would mean every zval has to carry in which namespace it was
defined inside. I wonder how that would affect the memory footprint of
PHP.

> If we had something like that, then perhaps there could be a
> "delegatable" visibility, which was the equivalent for "protected", but
> when delegating rather than inheriting, e.g.
>
> class Foo {
>      private int $a =3D 1;
>      delegatable int $b =3D 2;
> }
>
> class Bar {
>      private delegate Foo $foo;
>      public function __construct(Foo $foo) {
>          $this->foo =3D $foo;
>          echo $this->a; // Error: can't access private property of a
> different class
>          echo $this->b; // allowed: access is to a "delegatable"
> property, in a "delegated" context
>      }
> }

The Foo class has to decide who to give access to, otherwise it's the
same as public access.

Olle