How to get Product Attribute Options by attribute code in Magento 2.0

Question

I am trying to retrieve the list of dropdown attributes and check if the value exists (if it does i need to get the value and assign it to the product) and if it doesnt i will have to create it and get its value to assign it to the product.

$attribute = $this->objectManager->create('Magento\Eav\Model\Entity\Attribute');
$attributeId = $attribute->getIdByCode('catalog_product','manufacturer');
$model = $this->objectManager->create('Magento\Catalog\Model\ResourceModel\Eav\Attribute');
$model->load($attributeId);
print_r($model->getFrontendLabel());

Answer 1

Following Magento 2 guidelines, you should not use ObjectManager by yourself. Instead, you must use dependency injection. More info here

In your Block/Controller/Helper..., create a constructor and inject \Magento\Catalog\Api\ProductAttributeRepositoryInterface class. For example :

/**
 * @var \Magento\Catalog\Api\ProductAttributeRepositoryInterface $_productAttributeRepository
 */
protected $_productAttributeRepository;

/**
 * @param \Magento\Catalog\Api\ProductAttributeRepositoryInterface $productAttributeRepository
 */
public function __construct(\Magento\Catalog\Api\ProductAttributeRepositoryInterface $productAttributeRepository)
{
    $this->_productAttributeRepository = $productAttributeRepository;
}

Then, in your dedicated method, you want to call (PHPDoc added for clarity) :

/** @var \Magento\Eav\Api\Data\AttributeOptionInterface[] $manufacturerOptions */
$manufacturerOptions = $this->_productAttributeRepository->get('manufacturer')->getOptions();

You can now get options values and labels this way :

foreach ($manufacturerOptions as $manufacturerOption) {
    $manufacturerOption->getValue();  // Value
    $manufacturerOption->getLabel();  // Label
}