Create dropdown product attribute in Magento 2

Creating a dropdown product attribute in Magento 2 allows you to manage product data more efficiently and maintain consistent values across your catalog.

There are two ways to create the dropdown attribute in Magento.
1 -> Manually: Go to the admin panel, Store -> Attributes -> Product.
2 -> Programmatically.

In this guide, we’ll walk through the steps to create and assign a dropdown product attribute programmatically.

So let’s start :
Step 1: Create the AddProductAttribute.php file in the location Vendor\Module\Setup\Patch\Data

<?php

namespace Vendor\Module\Setup\Patch\Data;

use Magento\Framework\Setup\ModuleDataSetupInterface;
use Magento\Framework\Setup\Patch\DataPatchInterface;
use Magento\Eav\Setup\EavSetupFactory;
use Magento\Eav\Model\Entity\Attribute\ScopedAttributeInterface;
use Magento\Eav\Model\Entity\Attribute\SetFactory;
use Magento\Catalog\Model\Product;

class AddProductAttribute implements DataPatchInterface
{
    public const ATTRIBUTE_GROUP = "Test Group";
    public const ATTRIBUTE_CODE = "custom_dropdown";
    
    /**
     * @var ModuleDataSetupInterface
     */
    private $moduleDataSetup;

    /**
     * @var EavSetupFactory
     */
    private $eavSetupFactory;

    /**
     * @var SetFactory
     */
    private $attributeSetFactory;


    /**
     * @param ModuleDataSetupInterface $moduleDataSetup
     * @param EavSetupFactory $eavSetupFactory
     * @param SetFactory $attributeSetFactory
     */
    public function __construct(
        ModuleDataSetupInterface $moduleDataSetup,
        EavSetupFactory $eavSetupFactory,
        SetFactory $attributeSetFactory
    ) {
        $this->moduleDataSetup = $moduleDataSetup;
        $this->eavSetupFactory = $eavSetupFactory;
        $this->attributeSetFactory = $attributeSetFactory;
    }

    /**
     * @inheritdoc
     */
    public function apply()
    {
        $eavSetup = $this->eavSetupFactory->create(['setup' => $this->moduleDataSetup]);
        if ($eavSetup->getAttributeId(Product::ENTITY, self::ATTRIBUTE_CODE)) {
            return $this;
        }
        $eavSetup->addAttribute(
            Product::ENTITY,
            self::ATTRIBUTE_CODE,
            [
                'type' => 'int',
                'backend' => '',
                'frontend' => '',
                'label' => 'Attribute Label',
                'input' => 'select',
                'class' => '',
                'source' => \Vendor\Module\Model\Config\Source\Options::class,
                'global' => \Magento\Eav\Model\Entity\Attribute\ScopedAttributeInterface::SCOPE_STORE,
                'visible' => true,
                'required' => false,
                'user_defined' => true,
                'searchable' => false,
                'filterable' => false,
                'comparable' => false,
                'visible_on_front' => false,
                'used_in_product_listing' => true,
                'unique' => false,
                'apply_to' => 'simple,grouped,configurable,downloadable,virtual,bundle',
                'group' => self::ATTRIBUTE_GROUP,
            ]
        );


        // Assign attribute to ALL attribute sets under "Test Group" group
        $entityTypeId = $eavSetup->getEntityTypeId(Product::ENTITY);
        $attributeId  = $eavSetup->getAttributeId(Product::ENTITY, self::ATTRIBUTE_CODE);
        $attributeSets = $eavSetup->getAllAttributeSetIds($entityTypeId);

        foreach ($attributeSets as $attributeSetId) {
            $groupId = $eavSetup->getAttributeGroupId(
                $entityTypeId,
                $attributeSetId,
                self::ATTRIBUTE_GROUP
            );

            if (!$groupId) {
                $eavSetup->addAttributeGroup(
                    $entityTypeId,
                    $attributeSetId,
                    self::ATTRIBUTE_GROUP,
                    100
                );
                $groupId = $eavSetup->getAttributeGroupId(
                    $entityTypeId,
                    $attributeSetId,
                    self::ATTRIBUTE_GROUP
                );
            }

            $eavSetup->addAttributeToGroup(
                $entityTypeId,
                $attributeSetId,
                $groupId,
                $attributeId,
                100
            );
        }


        return $this;
    }

    /**
     * @inheritdoc
     */
    public static function getDependencies()
    {
        return [];
    }

    /**
     * @inheritdoc
     */
    public function getAliases()
    {
        return [];
    }
}

Step 2: Create the Options.php file in the location Vendor\Module\Model\Config\Source

Note: Options for the dropdown attribute can be added directly as an array. Here, we are using ‘source’ to add the options as follows :

<?php

namespace Vendor\Module\Model\Config\Source;

class Options extends \Magento\Eav\Model\Entity\Attribute\Source\AbstractSource
{
    /**
    * Get all options
    *
    * @return array
    */
    public function getAllOptions()
    {
        $this->_options = [
                ['label' => __('No'), 'value'=>'0'],
                ['label' => __('Yes'), 'value'=>'1'],
                ['label' => __('Other'), 'value'=>'2']
            ];

    return $this->_options;

    }

}

Step 3: Run the following command on your magento root directory.