Change Row Total for Quote Item whithout changing the Price

Question

I have tried to set a custom price for this purpose but it's getting multiplied by quantity. All I need to add an extra amount(like 50$) to each quote item after it's added to the cart. So it will be like this if have 2 products in the cart... First product Price 5.00$ qty is 10. Second Product Price 3.50$ qty is 20.

I want the calculation be like : (5.00 * 10 + 50) + (3.50 * 20 + 50) item 1 subtotal = 100. item 2 subtotal = 120. Total = 220.

For Magento 1 it was implemented in Sales_Quote_Item model in CalcRowTotal(). like this.. $baseTotal = $this->getBaseRowTotal() + $additionalCharges;

    $baseTotal = $this->getBaseRowTotal() + $additionalCharges; //$additionalCharges is the custom value that i want to add.
    $total = $this->getStore()->convertPrice($baseTotal);
    $this->setRowTotal($this->getStore()->roundPrice($total));
    $this->setBaseRowTotal($this->getStore()->roundPrice($baseTotal));

But in Magento 2 this is not working. Can anyone help ??

Answer 1

You can achieve this by using registry and observer, check below code

You have to override cart/add controller

\Magento\Checkout\Controller\Cart\Add

You can pass your formatted price in observer like below,

$baseTotal = $this->getBaseRowTotal() + $additionalCharges;

$this->_registry->register('price_values', $baseTotal);

Above is my code, you have to set your logic there.

And now we will use this registry in observer like below,

public function execute(\Magento\Framework\Event\Observer $observer)
{                           
    $items=$observer->getItems();        
    if($items){
        foreach($items as $item){                    
                if($customPrice=$this->registry->registry('price_values')){ 
                    $item->setCustomPrice($customPrice);
                    $item->setOriginalCustomPrice($customPrice);
                    $item->setPrice(null);
                    $item->setBasePrice(null);                        
                    $this->registry->unregister('price_value');
                }                 
            }                
        }
} 

Please check with above technique.