Using validation attributes

It is possible to add extra rules as attributes to properties of a data object:

class SongData extends Data
{
    public function __construct(
        #[Uuid()]
        public string $uuid,
        #[Max(15), IP, StartsWith('192.')]
        public string $ip,
    ) {
    }
}

These rules will be merged together with the rules that are inferred from the data object.

So it is not required to add the required and string rule, these will be added automatically. The rules for the above data object will look like this:

[
    'uuid' => ['required', 'string', 'uuid'],
    'ip' => ['required', 'string', 'max:15', 'ip', 'starts_with:192.'],
]

For each Laravel validation rule we've got a matching validation attribute, you can find a list of them here.

##Referencing route parameters

Sometimes you need a value within your validation attribute which is a route parameter. Like the example below where the id should be unique ignoring the current id:

class SongData extends Data
{
    public function __construct(
        public string $title,
        #[Unique('songs', ignore: new RouteParameterReference('song'))]
        public int $id,
    ) {
    }
}

If the parameter is a model and another property should be used, then you can do the following:

class SongData extends Data
{
    public function __construct(
        public string $title,
        #[Unique('songs', ignore: new RouteParameterReference('song', 'uuid'))]
        public string $uuid,
    ) {
    }
}

##Referencing other fields

It is possible to reference other fields in validation attributes:

class SongData extends Data
{
    public function __construct(
        public string $title,
        #[RequiredIf('title', 'Never Gonna Give You Up')]
        public string $artist,
    ) {
    }
}

These references are always relative to the current data object. So when being nested like this:

class AlbumData extends Data
{
    public function __construct(
        public string $album_name,
        public SongData $song,
    ) {
    }
}

The generated rules will look like this:

[
    'album_name' => ['required', 'string'],
    'songs' => ['required', 'array'],
    'song.title' => ['required', 'string'],
    'song.artist' => ['string', 'required_if:song.title,"Never Gonna Give You Up"'],
]

If you want to reference fields starting from the root data object you can do the following:

class SongData extends Data
{
    public function __construct(
        public string $title,
        #[RequiredIf(new FieldReference('album_name', fromRoot: true), 'Whenever You Need Somebody')]
        public string $artist,
    ) {
    }
}

The rules will now look like this:

[
    'album_name' => ['required', 'string'],
    'songs' => ['required', 'array'],
    'song.title' => ['required', 'string'],
    'song.artist' => ['string', 'required_if:album_name,"Whenever You Need Somebody"'],
]

##Rule attribute

One special attribute is the Rule attribute. With it, you can write rules just like you would when creating a custom Laravel request:

// using an array
#[Rule(['required', 'string'])] 
public string $property

// using a string
#[Rule('required|string')]
public string $property

// using multiple arguments
#[Rule('required', 'string')]
public string $property

##Creating your validation attribute

It is possible to create your own validation attribute by extending the CustomValidationAttribute class, this class has a getRules method that returns the rules that should be applied to the property.

#[Attribute(Attribute::TARGET_PROPERTY | Attribute::TARGET_PARAMETER)]
class CustomRule extends CustomValidationAttribute
{
    /**
     * @return array<object|string>|object|string
     */
    public function getRules(ValidationPath $path): array|object|string
    {
        return [new CustomRule()];
    }
}

Quick note: you can only use these rules as an attribute, not as a class rule within the static rules method of the data class.