Applying coupon codes via URL

Question

I was wondering if it was possible to allow a customer to apply a coupon code using a URL or URL params in Commerce 2. I haven’t been able to find any questions on stack exchange or on the web, but the scenario I’m trying to support is:

• Customer receives an email with a coupon code (includes a coupon code image that links to the storefront)

• Customer clicks a link which takes them to the store and automatically applies the coupon with a toast confirmation (e.g. store.com?coupon=somecouponcode)

• Customer adds purchasables to cart and when they go to the cart page, the coupon is already applied to cart lineitems without requiring them to manually input it themselves

Answer 1

The following code can be used in the init method of a custom module.

Event::on(
    View::class,
    View::EVENT_BEFORE_RENDER_PAGE_TEMPLATE,
    function($event) {
        // Check query string for coupon code
        $couponCode = Craft::$app->getRequest()->getQueryParam('coupon', null);

        if ($couponCode) {
            // Check there is a discount that has this coupon code
            $discount = Commerce::getInstance()->getDiscounts()->getDiscountByCode($couponCode);
            if ($discount) {
                $cart = Commerce::getInstance()->getCarts()->getCart();

                $cart->couponCode = $couponCode;
                Craft::$app->getElements()->saveElement($cart, false);
            }
        }

    }
);

Don't forget the following use statements at the top of the file.

use Craft;
use craft\commerce\Plugin as Commerce;
use craft\web\View;
use yii\base\Event;