How do I add a custom validator in my FormRequest?

Question

I have a rule (foobar) that is not built in to Laravel that I want to use within my extended FormRequest. How can I create a custom validator for t

Answer 1

It is possible to have your custom validation method by creating a validator property to your class and setting it to app('validator'). You can then with that property run extend, just like with the facade.

Create a __construct method and add this:

public function __construct() {
    $this->validator = app('validator');

    $this->validateFoobar($this->validator);
}

Then create a new method called validateFoobar that take the validator property as the first argument and run extend on that, just like with the facade.

public function validateFoobar($validator) {
    $validator->extend('foobar', function($attribute, $value, $parameters) {
        return ! MyModel::where('foobar', $value)->exists();
    });
}

More detail about extend is available here.

In the end, your FormRequest could look like this:

<?php namespace App\Http\Requests;

use App\Models\MyModel;
use App\Illuminate\Foundation\Http\FormRequest;

class MyFormRequest extends FormRequest {
    public function __construct() {
        $this->validator = app('validator');

        $this->validateFoobar($this->validator);
    }

    public function rules() {
        return [
            'id' => ['required', 'foobar']
        ];
    }

    public function messages() {
        return [
            'id.required' => 'You have to have an ID.',
            'id.foobar' => 'You have to set the foobar value.'
        ];
    }

    public function authorize() { return true; }

    public function validateFoobar($validator) {
        $validator->extend('foobar', function($attribute, $value, $parameters) {
            return ! MyModel::where('category_id', $value)->exists();
        });
    }
}