protected function getUserCurrency(Request $request)
    {
        // Check request for currency
        $currency = $request->get('currency');
        if ($currency && currency()->isActive($currency) === TRUE) {
            return $currency;
        }

        // Get currency from session
        $currency = $request->getSession()->get('igniter.currency');
        if ($currency && currency()->isActive($currency) === TRUE) {
            return $currency;
        }

        return null;
    }