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Date: Mon, 24 Mar 2025 11:20:03 +0200
Message-ID: <CAAwdEzBL_VR8ofZrFjKdKFE7dc54fKuZpwx7WsTusBtXit+e2A@mail.gmail.com>
Subject: Re: [PHP-DEV] Re: RFC: short and inner classes
To: Larry Garfield <larry@garfieldtech.com>
Cc: php internals <internals@lists.php.net>
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From: drealecs@gmail.com (=?UTF-8?Q?Alexandru_P=C4=83tr=C4=83nescu?=)

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On Sun, Mar 23, 2025 at 5:20=E2=80=AFPM Larry Garfield <larry@garfieldtech.=
com>
wrote:

>
> So, how would nested classes compare to fileprivate, in terms of ability
> to solve the problem space?  As I understand it, the goal is:
>
> 1. Classes that can be instantiated only by the class that uses them.
> 2. But can be returned from that class to a caller and reused as
> appropriate.
>


I think the one other difference is that nested classes can access private
variables or their outer classes.
Example:
```
class Polygon {
    private function __construct(private array $points) {}
    public function getPoints(): array {
        return $this->points;
    }
    public class Builder {
        private array $points =3D [];
        public function addPoint(Points $point): self {
            $this->points[] =3D $point;
            return $this;
        }
        public function build(): Polygon {
            if (count($this->points) < 3) {
                throw new InvalidArgumentException('A polygon must have at
least 3 points');
            }
            return new Polygon($this->points);
        }
    }
}
```
And it would be used like this:
```
$polygon =3D new Polygon::Builder()
    ->addPoint($point1)
    ->addPoint($point1)
    ->addPoint($point1)
    ->build();
```
With no way to create a Polygon otherwise, due to the private constructor.

-- Alex

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><div class=3D"gmail_quote gmail=
_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Sun, Mar 23, 202=
5 at 5:20=E2=80=AFPM Larry Garfield &lt;<a href=3D"mailto:larry@garfieldtec=
h.com">larry@garfieldtech.com</a>&gt; wrote:<br></div><blockquote class=3D"=
gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(20=
4,204,204);padding-left:1ex"><br>
So, how would nested classes compare to fileprivate, in terms of ability to=
 solve the problem space?=C2=A0 As I understand it, the goal is:<br>
<br>
1. Classes that can be instantiated only by the class that uses them.<br>
2. But can be returned from that class to a caller and reused as appropriat=
e.<br>=C2=A0=C2=A0</blockquote><div>=C2=A0</div><div>I think the one other =
difference is that nested classes can access private variables or their out=
er classes.<br>Example:</div><div>```</div><div><font face=3D"monospace">cl=
ass Polygon {<br>=C2=A0 =C2=A0 private function __construct(private array $=
points) {}<br>=C2=A0 =C2=A0 public function getPoints(): array {<br>=C2=A0 =
=C2=A0 =C2=A0 =C2=A0 return $this-&gt;points;<br>=C2=A0 =C2=A0 }<br>=C2=A0 =
=C2=A0 public class Builder {<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 private array =
$points =3D [];<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 public function addPoint(Poi=
nts $point): self {<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 $this-&gt;=
points[] =3D $point;<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 return $t=
his;<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 }<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 public=
 function build(): Polygon {<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 i=
f (count($this-&gt;points) &lt; 3) {<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 throw new InvalidArgumentException(&#39;A polygon must=
 have at least 3 points&#39;);<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 }<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 return new Polygon($this-&g=
t;points);<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 }<br>=C2=A0 =C2=A0 }<br>}</font><=
/div><div>```</div><div>And it would be used like this:</div><div>```</div>=
<div><font face=3D"monospace">$polygon =3D new=C2=A0Polygon::Builder()</fon=
t></div><div><font face=3D"monospace">=C2=A0 =C2=A0 -&gt;addPoint($point1)<=
/font></div><div><font face=3D"monospace">=C2=A0 =C2=A0 -&gt;addPoint($poin=
t1)</font></div><div><font face=3D"monospace">=C2=A0 =C2=A0 -&gt;addPoint($=
point1)</font></div><font face=3D"monospace">=C2=A0 =C2=A0 -&gt;build();</f=
ont><br class=3D"gmail-Apple-interchange-newline"><div>```</div><div>With n=
o way to create a Polygon=C2=A0otherwise, due to the private constructor.</=
div><div><br></div><div>-- Alex</div></div></div>

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