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Date: Sat, 15 Oct 2022 09:33:15 -0500
To: "php internals" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Casting array to any class
From: larry@garfieldtech.com ("Larry Garfield")

On Sat, Oct 15, 2022, at 6:18 AM, Gianni Gentile wrote:
> Hi,
>
> in my every day experience, using custom DTO classes and different API=
,=20
> I often write code to instantiate my objects from associative arrays.
>
> What are your thoughts on introduce the `(AnyType)` cast to instantiat=
e=20
> objects from associative array (or object properties also)?
>
> In my proposal, if AnyType implements __set_state(), casting should be=20
> syntactic sugar for:
>
>  =C2=A0=C2=A0=C2=A0 AnyType::_set_state((array) $data)
>
> just for (useless) example, consider DateTime or DateTimeImmutable (bo=
th=20
> have __set_state() implementation); when applied to objects of that=20
> type, we can write:
>
>  =C2=A0=C2=A0=C2=A0 $dt =3D new DateTime();
>
>  =C2=A0=C2=A0=C2=A0 $dtArray =3D (array) $dt; // 3 elements array
>
>  =C2=A0=C2=A0=C2=A0 $copyOfDt =3D (DateTime) $dtArray; // or simply $c=
opyOfDt =3D=20
> (DateTime) $dt;
>
> In case AnyType does not implements __set_state(), casting should crea=
te=20
> a new instance, assigning values to properties, taken from array value=
s=20
> with corresponding key (in a similar way class objects are created whe=
n=20
> row is fetched from database specifying PDO_FETCH_CLASS) eventually=20
> invoking __set() magic method for properties not declared;
>
> In this scenario,
>
>  =C2=A0=C2=A0=C2=A0 (object) ['one' =3D> 1, 'two' =3D> 2]
>
> and
>
>  =C2=A0=C2=A0=C2=A0 (StdClass) ['one' =3D> 1, 'two' =3D> 2]
>
> do exactly the same work.
>
>
> Reasons:
>
> - clear code
>
> - array to object conversion (casting) would be the simmetrical=20
> counterpart of object to array conversion

Most DTOs have a 1:1 match from constructor to properties.  In current P=
HP versions, that means they often look like this:

class Point
{
    public function __construct(
        public readonly int $x,
        public readonly int $y,
        public readonly int $z,
    ) {}
}

Which means, in current PHP versions, you can use named args and splat t=
o create one from an array.

$data =3D ['x' =3D> 1, 'y' =3D> 2, 'z' =3D> 3];

$point =3D new Point(...$data);

No casting necessary.

True, that's not true of all such classes, but certainly the plurality. =
 In the cases where it's not, an explicit named constructor (via a Trait=
 or otherwise) is a more self-documenting approach.

--Larry Garfield