Computed properties based on object state/input?

[ovp87]

Given the following example

<?php declare(strict_types = 1);

namespace App;

use Spatie\LaravelData\Data;
use Spatie\LaravelData\Lazy;

class Test extends Data
{
    public Lazy|bool $test1;
    public Lazy|int $test2;

    public function __construct(public string $name)
    {
        $this->test1 = Lazy::create(function(){
            return $this->name === 'hello world';
        });

        $this->test2 = Lazy::create(function(){
            return $this->name === 'hello world' 
                ? 1234 
                : 5678;
        });
    }
}

$test = \App\Test::validateAndCreate(['name' => 'hello world']);

$test2 fails validation (evaluated as required), while $test1 is set correctly.

I'm assuming i'm using it incorrectly, what i'm really trying to do is automatically set a property on the object, based on the input/state of the object, achieving something akin to computed properties in vue.
Ideally without it being possible to overwrite this property by passing in 'test1' => false.

Can anyone give me a pointer to the best way of doing this for this package?

[ovp87]

"Closest" i've come is something like this:

class Test extends Data
{
    #[Nullable]
    public readonly bool $test1;
    #[Nullable]
    public readonly int $test2;

    public function __construct(public string $name) {
        $this->test1 = $name === 'hello world';
        $this->test2 = $name === 'hello world' ? 1234 : 5678;
    }

}

[Nir-An]

Hi @ovp87

What about native '?' without #[Nullable]

class Test extends Data
{
    public readonly ?bool $test1;

    public readonly ?int $test2;

    public function __construct(public string $name) {
        $this->test1 = $name === 'hello world';
        $this->test2 = $name === 'hello world' ? 1234 : 5678;
    }

}

https://wiki.php.net/rfc/typed_properties_v2

[ovp87]

That would be "cleaner", however i run into Cannot modify readonly property issues when using readonly properties.
It's not clear to me how ?bool differs from using the nullable attribute.

[ejntaylor]

public function __construct()
    {
        [$projectName, $manifestFile] = explode(':', "{$this->name}:");
        $this->projectName = $projectName;
        $this->manifestFile = $manifestFile;
    }

Wondering how this is possible when using an existing parameter. Currently getting this Typed Property Exception:

\Project::$name must not be accessed before initialization

[rubenvanassche]

Have you already taken a look at optional properties? https://spatie.be/docs/laravel-data/v2/as-a-data-transfer-object/optional-properties

[XedinUnknown]

@rubenvanassche, it says

The value of artist will automatically be set to Optional. When you transform this data object to an array, it will look like this:

[
    'title' => 'Never gonna give you up'
]

But it doesn't say how to determine the value of Optional, and I don't understand how it becomes 'Never gonna give you up'.

Either way, that isn't the point for me. In my case, as a diligent developer, I have an enum that lists the possible values that the type property of my entity may have, and is used throughout the application. My OpenAPI specification uses a corresponding enum schema in order to allow keys from that enum, only those, and at least one:

type: object
minProperties: 1
propertyNames:
  $ref: MyEnum
additionalProperties:
  type: string

This is great, because in order to allow anothe property (all have the same type), I only need to add a new value to MyEnum.
How do I implement this using a DTO?

I can use an associative array e.g.

/* @var array<value-of<MyEnum>, string> */
public readonly array $names;

But now my DTO translates to having a property names, rather than having a bunch of properties - each one of my enum values.

Right now, I have to resort to adding a separate property to the DTO, one for each enum member.