How To Validate Minimum/Maximum Quantity On Product Page In Magento 2

In this blog, we validate product quantity while clicking add to cart in Magento 2.

On the product page, we can validate the maximum qty of products to add to the cart.

To achieve it we will follow some steps:

1. Create a custom module in Magento 2

We have created a module WebkulCustomModule.

To create a module you can follow the blog – How to Create Hello World Module in Magento

2. Create module configuration

We have created a module configuration for set product max qty for add to cart.

You can follow this to know more about the system.xml file in magento 2

https://devdocs.magento.com/guides/v2.3/config-guide/prod/config-reference-systemxml.html

etc/adminhtml/system.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <tab id="webkul" translate="label" sortOrder="10">
            <label>Webkul</label>
        </tab>
        <section id="Custom" translate="label" type="text" sortOrder="300" showInDefault="1" showInWebsite="1" showInStore="1">
            <label>Custom Module Settings</label>
            <!-- Assign section to tab -->
            <tab>webkul</tab>
            <resource>Webkul_CustomModule::custommodule_config</resource>
            <!-- create group for fields in section -->
            <group id="general_settings" translate="label" type="text" sortOrder="0" showInDefault="1" showInWebsite="1" showInStore="1">
                <label>General Settings</label>
                <field id="max_qty" translate="label" sortOrder="1" type="text" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Max Qty</label>
                </field>
            </group>
        </section>
    </system>
</config>

3. Need to create a plugin in our CustomModule in Magento 2

We have created a Plugin in our module.

There is a design pattern called ‘Interception’ used in Plugins.
Interception is inserting code dynamically without changing the original class behavior. In this process, code is dynamically inserted between the calling code and the target object.

To know more about plugins follow the blog – Magento2 – Create and Use Plugins

we have added the plugin code name and path in the di.xml file

etc/di.xml

<?xml version="1.0"?>
<!--
/**
 * Webkul Software.
 *
 * @category  Webkul
 * @package   Webkul_CustomModule
 * @author    Webkul
 * @copyright Copyright (c) Webkul Software Private Limited (https://webkul.com)
 * @license   https://store.webkul.com/license.html
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Catalog\Block\Product\View">
        <plugin name="Webkul_CustomModule::checkSellerMaxQty"             type="Webkul\CustomModule\Plugin\Block\ProductView" />
    </type>
</config>

4. Need to create a Plugin file

We have created a plugin file

Plugin/Block/ProductView.php

<?php
/**
 * Webkul Software.
 *
 * @category  Webkul
 * @package   Webkul_CustomModule
 * @author    Webkul
 * @copyright Copyright (c) Webkul Software Private Limited (https://webkul.com)
 * @license   https://store.webkul.com/license.html
 */
namespace Webkul\CustomModule\Plugin\Block;

use Magento\CatalogInventory\Api\StockRegistryInterface;

class ProductView
{
    /**
     * @var StockRegistryInterface
     */
    private $stockRegistry;

    /**
   * @var \Magento\Framework\App\Config\ScopeConfigInterface
   */ 
    protected $scopeConfig;

   /**
    * Construct
    *
    * @param StockRegistryInterface $stockRegistry
    * @param \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig
    */
    public function __construct(
        StockRegistryInterface $stockRegistry,
        \Magento\Framework\App\Config\ScopeConfigInterface $scopeConfig
    ) {
        $this->stockRegistry = $stockRegistry;
        $this->scopeConfig = $scopeConfig;
    }

    /**
     * Set Max limit on cart
     *
     * @param \Magento\Catalog\Block\Product\View $block
     * @param array $validators
     * @return array
     */
    public function afterGetQuantityValidators(
        \Magento\Catalog\Block\Product\View $block,
        array $validators
    ) {
        $stockItem = $this->stockRegistry->getStockItem(
            $block->getProduct()->getId(),
            $block->getProduct()->getStore()->getWebsiteId()
        );
        $productCartLimit = $this->scopeConfig->getValue('custom/general_settings/max_qty');
       
        $params = [];
        $params['minAllowed']  = (float)$stockItem->getMinSaleQty();
        if ($productCartLimit && $productCartLimit != "") {
            $params['maxAllowed'] = (float)$productCartLimit;
        } elseif ($stockItem->getMaxSaleQty()) {
            $params['maxAllowed'] = (float)$stockItem->getMaxSaleQty();
        }
        if ($stockItem->getQtyIncrements() > 0) {
            $params['qtyIncrements'] = (float)$stockItem->getQtyIncrements();
        }
        $validators['validate-item-quantity'] = $params;

        return $validators;
    }
}

Run these commands

php bin/magento setup:upgrade
php bin/magento setup:di:compile
php bin/magento cache:flush

Now we can check on the product page