Casting array to any class View as Markdown

Hi,

Am 15.10.22 um 13:18 schrieb Gianni Gentile:

Hi,

in my every day experience, using custom DTO classes and different API,
I often write code to instantiate my objects from associative arrays.

What are your thoughts on introduce the (AnyType) cast to instantiate
objects from associative array (or object properties also)?

In my proposal, if AnyType implements __set_state(), casting should be
syntactic sugar for:

    AnyType::_set_state((array) $data)

just for (useless) example, consider DateTime or DateTimeImmutable (both
have __set_state() implementation); when applied to objects of that
type, we can write:

    $dt = new DateTime();

    $dtArray = (array) $dt; // 3 elements array

    $copyOfDt = (DateTime) $dtArray; // or simply $copyOfDt =
(DateTime) $dt;

In case AnyType does not implements __set_state(), casting should create
a new instance, assigning values to properties, taken from array values
with corresponding key (in a similar way class objects are created when
row is fetched from database specifying PDO_FETCH_CLASS) eventually
invoking __set() magic method for properties not declared;

In this scenario,

    (object) ['one' => 1, 'two' => 2]

and

    (StdClass) ['one' => 1, 'two' => 2]

do exactly the same work.

Reasons:

• clear code

• array to object conversion (casting) would be the simmetrical
  counterpart of object to array conversion

I see your use case and I often have similar needs. Some thoughts:

• Are there any restrictions regarding the matching of array keys and
  the class attributes? What if there are additional keys in the array
  that do not have corresponding attributes? What if there are some
  attributes in the class that do not exist in the array?

• Can I forbid a class to be created by casting from an array? When I
  think about domain entities/aggregates, such a casting would allow to
  create an invalid state of the object without any checks. (Okay, we have
  similar issues when recreating them from a database via some ORM.)

BTW:

<?php declare(strict_types=1);

class A
{
private string $myPrivate = 'private';
protected string $myProtected = 'protected';
public string $myPublic = 'public';
}

$a = new A();

var_dump((array) $a);

?>

Will dump with modified array keys:

/home/thomas/test.php:12:
array(3) {
'\0A\0myPrivate' =>
string(7) "private"
'\0*\0myProtected' =>
string(9) "protected"
'myPublic' =>
string(6) "public"
}

So it's not as symmetric as intended.

Regards
Thomas

Hi,

in my every day experience, using custom DTO classes and different API,
I often write code to instantiate my objects from associative arrays.

What are your thoughts on introduce the (AnyType) cast to instantiate
objects from associative array (or object properties also)?

In my proposal, if AnyType implements __set_state(), casting should be
syntactic sugar for:

    AnyType::_set_state((array) $data)

just for (useless) example, consider DateTime or DateTimeImmutable (both
have __set_state() implementation); when applied to objects of that
type, we can write:

    $dt = new DateTime();

    $dtArray = (array) $dt; // 3 elements array

    $copyOfDt = (DateTime) $dtArray; // or simply $copyOfDt =
(DateTime) $dt;

In case AnyType does not implements __set_state(), casting should create
a new instance, assigning values to properties, taken from array values
with corresponding key (in a similar way class objects are created when
row is fetched from database specifying PDO_FETCH_CLASS) eventually
invoking __set() magic method for properties not declared;

In this scenario,

    (object) ['one' => 1, 'two' => 2]

and

    (StdClass) ['one' => 1, 'two' => 2]

do exactly the same work.

Reasons:

• clear code

• array to object conversion (casting) would be the simmetrical
  counterpart of object to array conversion

Most DTOs have a 1:1 match from constructor to properties. In current PHP 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 to create one from an array.

$data = ['x' => 1, 'y' => 2, 'z' => 3];

$point = new Point(...$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