Add additional select attributes to grouped product's child collection

Question

I am trying to add additional attributes to the collection that is created when getting a grouped product's associated simple products:

# Magento\GroupedProduct\Model\Product\Type\Grouped

public function getAssociatedProducts($product)
{
    if (!$product->hasData($this->_keyAssociatedProducts)) {
        $associatedProducts = [];

        $this->setSaleableStatus($product);

        $collection = $this->getAssociatedProductCollection(
            $product
        )->addAttributeToSelect(
            ['name', 'price',  'special_price', 'special_from_date', 'special_to_date']
        )->addFilterByRequiredOptions()->setPositionOrder()->addStoreFilter(
            $this->getStoreFilter($product)
        )->addAttributeToFilter(
            'status',
            ['in' => $this->getStatusFilters($product)]
        );

        foreach ($collection as $item) {
            $associatedProducts[] = $item;
        }

        $product->setData($this->_keyAssociatedProducts, $associatedProducts);
    }
    return $product->getData($this->_keyAssociatedProducts);
}

The attributes I would like to add are image-related ('image', 'small_image', 'thumbnail').

I put together a plugin that will redo the collection, but I'm getting an error that I'm passing the wrong type:

Uncaught TypeError: Argument 1 passed to Vendor\\Swatches\\Plugin\\GroupedSwatches::afterGetAssociatedProducts() must be an instance of Magento\\Catalog\\Model\\Product, instance of Magento\\GroupedProduct\\Model\\Product\\Type\\Grouped\\Interceptor given

Here is my (very inefficient) plugin method:

public function afterGetAssociatedProducts(\Magento\Catalog\Model\Product $product, $result)
{
    $associatedProducts = array();
    $collection = $product->getAssociatedProductCollection(
        $product
    )->addAttributeToSelect(
        ['name', 'price', 'special_price', 'special_from_date', 'special_to_date', 'image', 'small_image', 'thumbnail']
    )->addFilterByRequiredOptions()->setPositionOrder()->addStoreFilter(
        $this->getStoreFilter($product)
    )->addAttributeToFilter(
        'status',
        ['in' => $this->getStatusFilters($product)]
    );

    foreach ($collection as $item) {
        $associatedProducts[] = $item;
    }

    $product->setData($this->_keyAssociatedProducts, $associatedProducts);

    return $result;
}

Is this even the right approach for this?

Answer 1

For adding additional attributes for child in grouped product, add code like this to a Plugin/Model/Product/Type/GroupedPlugin.php file in your extension (this example assumes your extension is VendorName_ModuleName)

namespace VendorName\ModuleName\Model\Product\Type;

use \Magento\Catalog\Model\ResourceModel\Product\Link\Product\Collection;
use \Magento\GroupedProduct\Model\Product\Type\Grouped as Grouped;


class Grouped
{
    public function afterGetAssociatedProductCollection(Grouped $subject, Collection $result)
    {
        $result->addAttributeToSelect('attr1');
        $result->addAttributeToSelect('attr2');

        return $result;
    }
}

And add this code to an etc/frontend/di.xml file in your module:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">

    <type name="Magento\GroupedProduct\Model\Product\Type\Grouped">
        <plugin sortOrder="1" name="moduleNamePluginGrouped" type="VendorName\ModuleName\Plugin\Model\Product\Type\GroupedPlugin"/>
    </type>
</config>