Magento 2: Set product dropdown attribute

Question

I want to set a value to a dropdown attribute.

I try to use $product->setSize("M") but it is set to null.

Do I need to create the option of dropdown attribute ?

Answer 1

I am amused , you want dynamic drop-down for Product attribute then you should create custom attribute with dynamic Source: from Setup/UpgradeData.php script:

if (version_compare($context->getVersion(), '1.0.3') < 0) {
        //code to upgrade to 1.0.3
        $eavSetup->addAttribute(\Magento\Catalog\Model\Product::ENTITY, 'product_channel', [
            'type' => 'varchar',
            'label' => 'Size',
            'input' => 'select',
            'source' => 'Custom\Product\Model\Products\Attribute\Source\sizeattribute',
            'backend' => 'Magento\Eav\Model\Entity\Attribute\Backend\ArrayBackend',
            'required' => false,
            'sort_order' => 20,
            'global' => \Magento\Catalog\Model\ResourceModel\Eav\Attribute::SCOPE_GLOBAL,
            'group' => 'General',
            'visible' => true,
            'is_used_in_grid' => true,
            'is_visible_in_grid' => true,
            'is_filterable_in_grid' => true,
        ]);
    }

I hope it will help you.

Answer 2

If you want to add more options to dropdown/select attribute using code then you can do it by following steps.

Step 1 : Create construct method

protected $_eavSetupFactory;
protected $_storeManager;
protected $_attributeFactory;

public function __construct(
   Context $context,        
   \Magento\Eav\Setup\EavSetupFactory $eavSetupFactory,
   \Magento\Store\Model\StoreManagerInterface $storeManager,
   \Magento\Catalog\Model\ResourceModel\Eav\Attribute $attributeFactory
) {
     $this->_eavSetupFactory = $eavSetupFactory;
     $this->_storeManager = $storeManager;
     $this->_attributeFactory = $attributeFactory;
     parent::__construct($context);
  }

Step 2 : Create an array of options which you want to add to attribute

$attribute_arr = ['Yellow','White','Black'];

Step 3 : Load attribute by attribute code “color_test” to get attribute id

$attributeInfo=$this->_attributeFactory->getCollection()
           ->addFieldToFilter('attribute_code',['eq'=>"color_test"])
           ->getFirstItem();
$attribute_id = $attributeInfo->getAttributeId();

Step 4 : Now create attribute options array

  $option=array();
  $option['attribute_id'] = $attributeInfo->getAttributeId();
  foreach($attribute_arr as $key=>$value){
     $option['value'][$value][0] = $value;
     $option['value'][$value][1] = $value;
   }

Step 5 : Now add this option array to attribute

  $eavSetup = $this->_eavSetupFactory->create();
  $eavSetup->addAttributeOption($option);

Now execute this code, you will see the attribute with these options in Magento.

Answer 3

You can not set value of dropdown attribute like this as value you are trying to set M it is a label and not the value. To set size M to the product you have to get the Value for the Size M and then set that value to the product.

You can check this answer to get Option Value by Label.