Cviebrock\EloquentSluggable\Services\SlugService::generateSlug PHP Method

    protected function generateSlug($source, array $config, $attribute)
    {
        $separator = $config['separator'];
        $method = $config['method'];
        $maxLength = $config['maxLength'];
        if ($method === null) {
            $slugEngine = $this->getSlugEngine($attribute);
            $slug = $slugEngine->slugify($source, $separator);
        } elseif (is_callable($method)) {
            $slug = call_user_func($method, $source, $separator);
        } else {
            throw new \UnexpectedValueException('Sluggable "method" for ' . get_class($this->model) . ':' . $attribute . ' is not callable nor null.');
        }
        if (is_string($slug) && $maxLength) {
            $slug = mb_substr($slug, 0, $maxLength);
        }
        return $slug;
    }