How to change the price in quote while adding product to cart?

Question

I want to apply a custom price for the current order. I read that I should use sales_quote_add_item, But its looks like I am doing something wrong. I found some tutorials for magento1 but not for Magento 2. So please let me know what I am doing wrong.

app/code/Myvendor/HelloMagento/etc/adminhtml/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="sales_quote_add_item">
        <observer name="change_hello_magento_display" instance="Myvendor\Addtocart\Observer\Change" />
    </event>
 </config>

app/code/Myvendor/HelloMagento/Observer/Change.php

<?php
namespace Myvendor\Addtocart\Observer;

class Change implements \Magento\Framework\Event\ObserverInterface
{
    public function execute(\Magento\Framework\Event\Observer $observer)
    {
        $event = $observer->getEvent();
        $quote_item = $event->getQuoteItem();
        $new_price = 987;
        $quote_item->setOriginalCustomPrice($new_price);
        $quote_item->save();
    }
}

Let me know please what I am doing wrong. I want to achieve the same thing for Magento 2 given on below link for magento1.

https://stackoverflow.com/questions/9721583/changing-the-price-in-quote-while-adding-product-to-cart-magento

Answer 1

Please follow the below steps:

Step-1: Create an events.xml in the following below path

Note: Here i am considering the module called Ewall_Pricecalculations

app/code/Ewall/Pricecalculations/etc/frontend/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="Ewall_Pricecalculations_Addtocart" instance="Ewall\Pricecalculations\Observer\PricecalculationsAfterAddtoCart" />
</event>
</config>

Step-2: Next Create a file in the name of PricecalculationsAfterAddtoCart.php keep the below code as shown below.

<?php
namespace Ewall\Pricecalculations\Observer;
use Magento\Framework\Event\ObserverInterface;
use Magento\Framework\App\RequestInterface;
 
class PricecalculationsAfterAddtoCart implements ObserverInterface
{
     
public function execute(\Magento\Framework\Event\Observer $observer) 
{
            $writer = new \Zend\Log\Writer\Stream(BP.'/var/log/stackexchange.log');
            $logger = new \Zend\Log\Logger();
            $logger->addWriter($writer);
            /* Code here */
            $quote_item = $observer->getEvent()->getQuoteItem();
            $price = 400; //set your price here
            $quote_item->setCustomPrice($price);
            $quote_item->setOriginalCustomPrice($price);
            $quote_item->getProduct()->setIsSuperMode(true);

            $logger->info("success !!!!");
            
    }
}

Step 3: please use php bin/magento setup:di:compile

clear cache and page_cache and check the same in the frontend.

Answer 2

Old question, and posted answer is valid for sure

Just wanted to point that the mentioned event (sales_quote_add_item) in question is available in Magento2, and it works fine for the asked customization with very few code

public function execute(\Magento\Framework\Event\Observer $observer)
{
    // your logic to get $yourPrice
    $quoteItem = $observer->getEvent()->getQuoteItem();
    $quoteItem->setOriginalCustomPrice($yourPrice);
}

Note that you shouldn't save() QuoteItem object