Order::getDeliveryCost PHP 메소드

    public function getDeliveryCost()
    {
        $cost = $this->delivery_price;
        if ($this->isCouponsAvailable()) {
            $validCoupons = $this->getValidCoupons($this->getCouponsCodes());
            foreach ($validCoupons as $coupon) {
                if ($coupon->free_shipping) {
                    $cost = 0;
                }
            }
        }
        return $cost;
    }