How to update order grand total via controller in Magento 2.2.2?

Question

I am trying to update the order's grand total via a controller.

Here is my controller's code:

<?php

namespace Company\Vendor\Controller\Index;

use Magento\Framework\App\Action\Action;
use Magento\Framework\App\Action\Context;

class Index extends Action
{
    protected $_checkoutSession;

    /**
     * @var \Magento\Quote\Api\CartRepositoryInterface
     */
    protected $_quoteRepository;

    public function __construct(
        Context $context,
        \Magento\Checkout\Model\Session $checkoutSession,
        \Magento\Quote\Api\CartRepositoryInterface $quoteRepository
    ) {
        parent::__construct($context);
        $this->_checkoutSession = $checkoutSession;
        $this->_quoteRepository = $quoteRepository;
    }

    public function execute()
    {

         $this->_quoteRepository->get($this->_checkoutSession->getQuoteId());

         $quote = $this->_checkoutSession->getQuote();

         $grand_total = $quote->getGrandTotal(); // It contains correct order grand total

         $new_grand_total = $grand_total + 100; // Adding 100 to order total

         $quote->setGrandTotal($new_grand_total);

         $quote->collectTotals();

         $this->_quoteRepository->save($quote);

         echo $quote->getGrandTotal();
    }
}

Above code is not updating the grand total.

Answer 1

Use collectTotals() method to re calculate totals

Try this

protected $_checkoutSession;

protected $quoteRepository;

public function __construct(
    ...
    \Magento\Checkout\Model\Session $checkoutSession,
    \Magento\Quote\Api\CartRepositoryInterface $quoteRepository
    ...
) {
    $this->_checkoutSession = $checkoutSession;
    $this->quoteRepository = $quoteRepository;
}


public function execute()
{
    $this->quoteRepository->get($this->_checkoutSession->getQuoteId());
    $quote = $this->_checkoutSession->getQuote();

    $grandTotal = "200"; // Set your grand total
    $this->_checkoutSession->getQuote()->setGrandTotal($grandTotal);
    $this->quoteRepository->save($quote->collectTotals());

    echo $quote->getGrandTotal();
}

Answer 2

You cannot update grand total, in such way. In magento, grand total is basically depends on cart item price and discount and tax calculation etc. So you cannot update the grand total.

I guess that you want implement concept like Extra Fee, Then you can extension like:

https://github.com/magecomp/magento2-extra-fee

https://github.com/sivajik34/Custom-Fee-Magento2

etc.