Magento 2 : How to Override /vendor/magento/module-quote/Model/Quote/Address/Total/Grand.php

Question

Not able to override grand.php file can anyone help me out.

Answer 1

You can create di.xml in etc/di.xml or if you want it to be area specific you can put in etc/frontend/di.xml or which ever area you want to override. Example of global preference app/code/StackoverFlow/GrandOverride/etc/di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="Magento\Quote\Model\Quote\Address\Total\Grand"
                type="StackoverFlow\GrandOverride\Model\Quote\Address\Total\Grand"/>
</config>  

and in file app/code/StackoverFlow/GrandOverride/Model/Quote/Address/Total/Grand.php you can override methods of the file

<?php

namespace StackoverFlow\GrandOverride\Model\Quote\Address\Total;

class Grand extends \Magento\Quote\Model\Quote\Address\Total\Grand
{

}

As you want to update public method i would suggest to use a plugin . You can it by adding below code in app/code/StackoverFlow/GrandOverride/etc/di.xml(remove preference you added before )

and in plugin class **StackoverFlow\GrandOverride\Plugin\PrecisionUpdate**

<?php


namespace StackoverFlow\GrandOverride\Plugin;

use Magento\Quote\Api\Data\ShippingAssignmentInterface;
use Magento\Quote\Model\Quote;
use Magento\Quote\Model\Quote\Address\Total;
use Magento\Quote\Model\Quote\Address\Total\Grand;
use Magento\Quote\Model\ShippingAssignment;

class PrecisionUpdate
{

    /**
     * @param Grand $subject
     * @param Grand $result
     * @param Quote $subject
     * @param Grand $result
     * @param ShippingAssignmentInterface $subject
     * @param Grand $result
     * @param Total $subject
     * @param Grand $result
     * @return Grand
     */
    public function afterCollect(Grand $subject, Grand $result, Quote $quote, ShippingAssignment $shippingAssignment, Total $total)
    {
        $grandTotal = $this->priceRounder->roundPrice($total->getGrandTotal(), 0);
        $baseGrandTotal = $this->priceRounder->roundPrice($total->getBaseGrandTotal(), 0);

        $total->setGrandTotal($grandTotal);
        $total->setBaseGrandTotal($baseGrandTotal);
        return $result;
    }
}

Update the plugin logic as you require , i have not tested the code . And hope you have created a new module , this code will not be executed untill you register your module . you can find details here https://devdocs.magento.com/videos/fundamentals/create-a-new-module/