Inject a class when extending the CatalogWidget component

Question

I want to extend the Catalog Widget to filter Out Of Stock products.

To do this, I have created a component to extend the Catalog Widget's ProductsList class, which contains the following code to replace its createCollection function.

class ProductsList extends \Magento\CatalogWidget\Block\Product\ProductsList
{

    public function createCollection(
    )
    {
        /** @var $collection \Magento\Catalog\Model\ResourceModel\Product\Collection */
        $collection = $this->productCollectionFactory->create();
        $objectManager = \Magento\Framework\App\ObjectManager::getInstance();
        $this->_stockFilter = $objectManager->create('Magento\CatalogInventory\Helper\Stock');
        $this->_stockFilter->addInStockFilterToCollection($collection);

        ... CODE CONTINUES AS PER THE FUNCTION IN app\vendor\magento\module-catalog-widget\Block\Product\ProductsList.php

        return $collection;
    }

} 

This works as I want it to. However, I know we should not use the object manager to load Magento\CatalogInventory\Helper\Stock

I've tried adding a __construct function, but this just causes a "Type Error occurred when creating object" error.

How should I be loading the Stock helper?

Answer 1

You should leverage dependency injection. Don't forget to empty generated directory to refresh generated code.

<?php

class ProductsList extends \Magento\CatalogWidget\Block\Product\ProductsList
{

    /**
     * @var \Magento\CatalogInventory\Helper\Stock
     */
    protected $_stockFilter;

    /**
     * ProductsList constructor.
     *
     * @param \Magento\Catalog\Block\Product\Context                         $context
     * @param \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory
     * @param \Product\Visibility                                            $catalogProductVisibility
     * @param \Magento\Framework\App\Http\Context                            $httpContext
     * @param \Magento\Rule\Model\Condition\Sql\Builder                      $sqlBuilder
     * @param \Magento\CatalogWidget\Model\Rule                              $rule
     * @param \Magento\Widget\Helper\Conditions                              $conditionsHelper
     * @param \Magento\CatalogInventory\Helper\Stock                         $stockFilter
     * @param array                                                          $data
     * @param \Magento\Framework\Serialize\Serializer\Json|null              $json
     * @param \Magento\Framework\View\LayoutFactory|null                     $layoutFactory
     * @param \Magento\Framework\Url\EncoderInterface|null                   $urlEncoder
     */
    public function __construct(
        \Magento\Catalog\Block\Product\Context $context,
        \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory $productCollectionFactory,
        Product\Visibility $catalogProductVisibility,
        \Magento\Framework\App\Http\Context $httpContext,
        \Magento\Rule\Model\Condition\Sql\Builder $sqlBuilder,
        \Magento\CatalogWidget\Model\Rule $rule,
        \Magento\Widget\Helper\Conditions $conditionsHelper,
        \Magento\CatalogInventory\Helper\Stock $stockFilter,
        array $data = [],
        \Magento\Framework\Serialize\Serializer\Json $json = null,
        \Magento\Framework\View\LayoutFactory $layoutFactory = null,
        \Magento\Framework\Url\EncoderInterface $urlEncoder = null
    ) {
        parent::__construct(
            $context,
            $productCollectionFactory,
            $catalogProductVisibility,
            $httpContext,
            $sqlBuilder,
            $rule,
            $conditionsHelper,
            $data,
            $json,
            $layoutFactory,
            $urlEncoder
        );
        $this->_stockFilter = $stockFilter;
    }

    public function createCollection()
    {
        /** @var $collection \Magento\Catalog\Model\ResourceModel\Product\Collection */
        $collection = $this->productCollectionFactory->create();
        $this->_stockFilter->addInStockFilterToCollection($collection);

        //... CODE CONTINUES AS PER THE FUNCTION IN app\vendor\magento\module-catalog-widget\Block\Product\ProductsList.php

        return $collection;
    }

}