Custom Dynamic Validation Rules for Laravel 5.5+

readme.md

This gist will help understand custom (artisan make:rule MyRule) dynamic (rules that require more context than just the attribute and value) validation rules for Laravel 5.5+.

StringIsLengthRule.php

<?php

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;

class StringIsLengthRule implements Rule
{
    protected $length;
    protected $message = 'The string must be greater than the length';

    public function __construct($length)
    {
        $this->length = $length;
    }

    public function passes($attribute, $value)
    {
        if (!$this->length || $this->length <= 0) {
            $this->message = 'The length has to be greater than zero to validate the string';
            return false;
        }

        return strlen($value) > $this->length;
    }

    public function message()
    {
        return $this->message;
    }
}

StringTesterController.php

<?php

namespace App\Http\Controllers;

use App\Http\Requests\StringTesterRequest;

class StringTesterController extends Controller
{
    public function form()
    {
        /**
         * Assume the form is:
         * <form method="POST" action="/string-tester">
         *     {{ csrf_field() }}
         *     Length: <input name="length"><br>
         *     String: <input name="string"><br>
         *     <button>Submit</button>
         * </form>
         */
        return view('form');
    }

    public function process(StringTesterRequest $request)
    {
        // reshow form, the form also has dump($request) in it for demonstration
        return view('form', compact('request'));
    }
}

StringTesterRequest.php

<?php

namespace App\Http\Requests;

use App\Rules\StringIsLengthRule;
use Illuminate\Foundation\Http\FormRequest;

class StringTesterRequest extends FormRequest
{
    public function authorize()
    {
        return true;
    }

    public function rules()
    {
        $rules = [
            'length' => 'required|numeric',
            'string' => [
                'required',
                new StringIsLengthRule($this->request->get('length'))
            ],
        ];
        return $rules;
    }
}