How can I use a custom source model for a multiselect product attribute in Magento 2

Question

I've created an attribute in Magento 2 of the type multiselect and now I want to have it populated by a custom source model.

Now I remember from Magento 1 that when you want to do this, you had to manually edit the attribute in the database and set the source_model to the path of the source model.

However, when I do this in Magento 2, I get an error. I changed source_model in eav_attribute to Vendor\Module\Model\Config\Source\Product\Attributes, but when I want to edit the product in the admin, I get the following error:

Fatal error: Uncaught Error: Call to undefined method Vendor\Module\Model\Config\Source\Product\Attributes::setAttribute() in .../vendor/magento/module-eav/Model/Entity/Attribute/AbstractAttribute.php:547
Stack trace: #0 .../var/generation/Magento/Catalog/Model/ResourceModel/Eav/Attribute/Interceptor.php(1129): Magento\Eav\Model\Entity\Attribute\AbstractAttribute->getSource()
#1 .../vendor/magento/module-backend/Block/Widget/Form.php(232): Magento\Catalog\Model\ResourceModel\Eav\Attribute\Interceptor->getSource()
#2 .../vendor/magento/module-backend/Block/Widget/Form.php(201): Magento\Backend\Block\Widget\Form->_applyTypeSpecificConfig('multiselect', Object(Magento\Framework\Data\Form\Element\Multiselect), Object(Magento\Catalog\Model\ResourceModel\Eav\Attribute\Interceptor))
#3 .../vendor/magento/module-catalog/Block/Adminhtml/Product/Edit/Tab/Attributes.php(51): Magento\Backend\Block\Widget\Form->_setFieldset(Array, Object(Magento\Framework\Data\Form\El in .../vendor/magento/module-eav/Model/Entity/Attribute/AbstractAttribute.php on line 547

Does anyone know how I can create a product attribute with a custom source model?

Edit:

Current Source Model:

use Vendor\Module\Model\Config\Source\AbstractSource;
use Magento\Catalog\Model\ResourceModel\Eav\AttributeFactory;
use Magento\Eav\Model\Entity\Attribute;
use Magento\Eav\Model\Entity\TypeFactory;
/**
 * Class Attributes
 */
class Attributes extends AbstractSource
{
 /**
 * @var AttributeFactory
 */
 protected $attributeFactory;
 /**
 * @var TypeFactory
 */
 protected $eavTypeFactory;
 /**
 * Attributes constructor.
 * @param AttributeFactory $attributeFactory
 @param TypeFactory $typeFactory
 */
 public function __construct(
 AttributeFactory $attributeFactory,
 TypeFactory $typeFactory
 )
 {
 $this->attributeFactory = $attributeFactory;
 $this->eavTypeFactory = $typeFactory;
 }
 /**
 * @return array
 */
 public function toArray()
 {
 $arr = [];
 $entityType = $this->eavTypeFactory->create()->loadByCode('catalog_product'); 
 $collection = $this->attributeFactory->create()->getCollection();
 $collection->addFieldToFilter('entity_type_id', $entityType->getId());
 $collection->setOrder('attribute_code');
 /** @var Attribute $attribute */
 foreach ($collection as $attribute) {
 $arr[$attribute->getAttributeId()] = $attribute->getFrontendLabel();
 }
 return $arr;
 }
}

Class Vendor\Module\Model\Config\Source\AbstractSource:

namespace Vendor\Module\Model\Config\Source;
abstract class AbstractSource implements \Magento\Framework\Option\ArrayInterface
{
 /**
 * Options getter
 * @return array
 */
 final public function toOptionArray()
 {
 $arr = $this->toArray();
 $ret = [];
 foreach ($arr as $key => $value) {
 $ret[] = [
 'value' => $key,
 'label' => $value
 ];
 }
 return $ret;
 }
 /**
 * Get options in "key-value" format
 * @return array
 */
 public function toArray()
 {
 return [];
 }
}

• Ryan Hoerr: Post your current source model code.
• Giel Berkers: I've added my source model and the abstract class it extends. The abstract class is nothing more than a method that generates the toOptionArray() output.

Answer 1

I got it! It turns out that multiselect uses the backend model Magento\Eav\Model\Entity\Attribute\Backend\ArrayBackend. For this reason, the source model, must also take EAV into account. How can we do this? Simple: just extend your source model from Attribute\Source\AbstractSource and implement the getAllOptions()-method (which returns a 2-dimensional array with value and label-keys:

/**
 * @return array
 */
public function getAllOptions()
{
 $arr = $this->toArray();
 $ret = [];
 foreach ($arr as $key => $value) {
 $ret[] = [
 'value' => $key,
 'label' => $value
 ];
 }
 return $ret;
}

That's it! Enjoy using your custom source model for multiselect attributes.

Answer 2

<?php
/**
 * Created by PhpStorm
 * User: moazzam
 * Date: 31/10/22
 * Time: 7:59 AM
 */
namespace NbrolMarket\LocalMarket\Model\Config;
use Magento\Eav\Model\Entity\Attribute\Source\AbstractSource;
use NbrolMarket\LocalMarket\Model\ResourceModel\Market\CollectionFactory as MarketCollectionFactory;
/**
 * Create market options
 *
 * Class MarketOptions
 */
class MarketOptions extends AbstractSource
{
 /**
 * @var MarketCollectionFactory
 */
 private MarketCollectionFactory $marketCollectionFactory;
 /**
 * @param MarketCollectionFactory $marketCollectionFactory
 */
 public function __construct(MarketCollectionFactory $marketCollectionFactory)
 {
 $this->marketCollectionFactory = $marketCollectionFactory;
 }
 /**
 * Retrieve All options
 *
 * @return array
 */
 public function getAllOptions()
 {
 $marketCollection = $this->marketCollectionFactory->create();
 $marketCollection->addFieldToSelect("*")->load()->getItems();
 if ($marketCollection->getSize() > 0){
 $options[] = ['label' => __('--Select--'), 'value' => ''];
 foreach ($marketCollection as $markets){
 $name = __($markets->getData('name'));
 $code = $markets->getData("code");
 $options[] = [
 'label'=> $name ,'value'=> $code
 ];
 }
 return $options;
 }
 }
}