Validator::extend for custom validation rules laravel 5.5

Laravel 5.5 will introduce support for custom validation rule objects as an alternative to using Validator::extend for custom validation rules.

To define a custom validation rule, implement the Illuminate\Contracts\Validation\Rule interface or use a Closure. The custom rule is then used directly in a validator.

An example of a custom object validation rule might look something like:

use Illuminate\Contracts\Validation\Rule;

class CowbellValidationRule implements Rule
{
    public function passes($attribute, $value)
    {
        return $value > 10;
    }

    public function message()
    {
        return ':attribute needs more cowbell!';
    }
}

With the custom rule defined, you might use it in your controller validation like so:

public function store()
{
    // Validation message would be "song needs more cowbell!"
    $this->validate(request(), [
        'song' => [new CowbellValidationRule]
    ]);
}

The same rule as a Closure would look something like the following.

public function store()
{
    $this->validate(request(), [
        'song' => [function ($attribute, $value, $fail) {
            if ($value <= 10) {
                $fail(':attribute needs more cowbell!');
            }
        }]
    ]);
}

The custom rule examples will not run if the song field is empty or isn’t present in the request. If you want a custom validation object to run even with the value is empty, you need to use the ImplicitRule contract.

use Illuminate\Contracts\Validation\ImplicitRule;

class CowbellValidationRule implements ImplicitRule
{
    public function passes($attribute, $value)
    {
        return $value > 10;
    }

    public function message()
    {
        return ':attribute needs more cowbell!';
    }
}

Custom validation rule objects will be an excellent alternative to Validator::extend() style custom rules if you prefer to organize custom rules in classes. Also, jumping to the rule source code from a validator can be more convenient than searching for a custom string-based rule defined with Validator::extend.

The Closure style custom validation rules will be nice for simple one-off needs and make it really convenient to experiment with custom validation rules without leaving the controller. You could use a Closure to experiment with a custom rule and then move it to an object if the rule proves useful.

Check out the pull request files to see how this feature was implemented and tested.