function convert(): bool
    {
        if (!is_string($this->value)) {
            $this->result = $this->value;
        }
        else {
            switch (strtolower($this->value)) {
                case '1':
                case 'true':
                case 'on':
                case 'yes':
                case 'y':
                    $this->result = true;
                default:
                    $this->result = false;
            }
        }

        return $this->result;
    }