[ 'required', function (string $attribute, mixed $value, Closure $fail) { $processManagerExists = $this->service->server->processManager(); if ($processManagerExists) { $fail('You already have a process manager service on the server.'); } }, ], ]; } public function deletionRules(): array { return [ 'service' => [ function (string $attribute, mixed $value, Closure $fail) { $hasQueue = $this->service->server->queues()->exists(); if ($hasQueue) { $fail('You have queue(s) on the server.'); } }, ], ]; } }