I know I asked the question once before, but i got no answer, so I try it again and hope for an answer this time. I also saw some other guys that tried to get an answer for this question, but none of them got one, so i need your help.

I would like to set a custom discount price to an existing cart/quote in my controller.

To give you an example, if the customer clicks a button in the cart he will get a random discount price. But now how can I achieve to add this specific disount price to the cart and quote in the controller?

I would appreciate if you could help me with this question.


This can be achieved by using event. use event checkout_cart_product_add_after. Let have an Observer with name AddToCart.php. We would be needing events.xml ofcourse for letting magento2 know.

let makes a file etc/events.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="checkout_cart_product_add_after">
        <observer name="vendor_catalogevent" instance="Vendor\Module\Observer\Product\CustomOption\PriceRule\Addtocart" />

Defining Observer , make a file in Observer/AddToCart.php

namespace Vendor\Module\Observer\Product\CustomOption\PriceRule;

use Magento\Catalog\Model\ProductFactory;

 * Class Addtocart
 * @package Vendor\Module\Observer\Product\CustomOption\PriceRule
class Addtocart implements \Magento\Framework\Event\ObserverInterface {

   * @var \Magento\Framework\App\RequestInterface
  protected $_request;

   * @var \Magento\Store\Model\StoreManagerInterface
  protected $_storeManager;

   * @var \Magento\Catalog\Model\Product
  protected $_product;

  public function __construct(
        \Magento\Catalog\Model\Product $product,
        \Magento\Store\Model\StoreManagerInterface $storeManager,
        \Magento\Framework\App\RequestInterface $request
      $this->_product                 = $product;
      $this->_storeManager            = $storeManager;
      $this->_request                 = $request;

   * @param \Magento\Framework\Event\Observer $observer
   * @throws \Magento\Framework\Exception\NoSuchEntityException
  public function execute(\Magento\Framework\Event\Observer $observer)
      $item = $observer->getEvent()->getData('quote_item');
      $item = ( $item->getParentItem() ? $item->getParentItem() : $item );
      $percentFactor = 0.2 //giving 20% discount
      $sku = $item->getSku();
      $productCollection = $this->_product->loadByAttribute('sku', $sku);
      $productPriceBySku = $productCollection->getPrice();
      $customPrice = $productPriceBySku * $percentFactor; // custom price

Let me know if this solves your problem.

Thank you.

| improve this answer | |
  • As I said I want to achieve this in a controller and not in a observer, i found a lot of solutions using an observer, but I just can't use an observer. – Felix Schönherr Oct 28 '19 at 14:40
  • Then you should override AddProduct function which is present in Magento\Checkout\Model\Cart and add your logic right before checkout_cart_product_add_after event dispatch. – Ali Hussain Oct 28 '19 at 15:13
  • Sorry, but this will also not help – Felix Schönherr Oct 29 '19 at 8:03

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