Override a model not working Magento 2

Question

I tried to override a model in Magento\Quote\Model\Cart\Data\CartItem but I cannot override it.

here is my 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\Cart\Data\CartItem" type="Vendor\AddProductWithVendorGraphQl\Model\Cart\Data\CartItem" />
</config>

and this is my class

class CartItem extends \Magento\Quote\Model\Cart\Data\CartItem
{

        /**
     * @var string
     */
    private $sku;

    /**
     * @var float
     */
    private $quantity;


    /**
     * @var string
     */
    private $parentSku;

    /**
     * @var SelectedOption[]
     */
    private $selectedOptions;

    /**
     * @var EnteredOption[]
     */
    private $enteredOptions;

    /**
     * @param string $sku
     * @param float $quantity
     * @param string|null $parentSku
     * @param array|null $selectedOptions
     * @param array|null $enteredOptions
     */
    public function __construct(
        string $sku,
        float $quantity,
        string $parentSku = null,
        array $selectedOptions = null,
        array $enteredOptions = null
    ) {
        $this->sku = $sku;
        $this->quantity = $quantity;
        $this->parentSku = $parentSku;
        $this->selectedOptions = $selectedOptions;
        $this->enteredOptions = $enteredOptions;
    }
    public function getQuantity(): float
    {
        var_dump('tes');die();
    }

I've tried to use plugins too. But it still didn't work. Can anyone help me?

Answer 1

Please try with the below code.

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */    

namespace Magento\Quote\Model\Cart\Data;

class CartItem extends \Magento\Quote\Model\Cart\Data\CartItem
{

    /**
     * @var string
     */
    private $sku;

    /**
     * @var float
     */
    private $quantity;


    /**
     * @var string
     */
    private $parentSku;

    /**
     * @var SelectedOption[]
     */
    private $selectedOptions;

    /**
     * @var EnteredOption[]
     */
    private $enteredOptions;

    /**
     * @param string $sku
     * @param float $quantity
     * @param string|null $parentSku
     * @param array|null $selectedOptions
     * @param array|null $enteredOptions
     */
    public function __construct(
        string $sku,
        float $quantity,
        string $parentSku = null,
        array $selectedOptions = null,
        array $enteredOptions = null
    ) {
        $this->sku = $sku;
        $this->quantity = $quantity;
        $this->parentSku = $parentSku;
        $this->selectedOptions = $selectedOptions;
        $this->enteredOptions = $enteredOptions;
        
        parent::__construct($sku, $quantity, $parentSku, $selectedOptions, $enteredOptions);
        //or
        parent::__construct($sku, $quantity, null, null, null);
    }
    public function getQuantity(): float
    {
        var_dump('tes');die();
    }

}

Might be the issue of you can't pass the parent argument.

Answer 2

I was struggling to understand the same here this week.

You probably already realized the "preference" method won't work for this class. It's because Magento doesn't load that class or its factory through dependency injection. I don't know why but for this specific class Magento is not following the design patterns.

$cartItems[] = (new CartItemFactory())->create($cartItemData);

You'll be able to solve that by just overriding the resolver.

Magento\QuoteGraphQl\Model\Resolver\AddProductsToCart

Then you can use DI to inject a custom factory class and build what you want.