Add category IDs to product collection

Question

I am injecting this collection into my model:

\Magento\Reports\Model\ResourceModel\Product\Collection $prodCollection

I use it to create an array of all products but I want to add the products category ids to the results.

I tried:

$prodItems = $this->prodCollection->addFieldToSelect('*')->addCategoryIds()->getData();

This doesn't include the category IDs in results. I am trying to avoid having to load the product through the product repository and calling the method to get categories on every single product as that would be a very expensive operation.

Whats the cheapest way to get the product categories?

Answer 1

    $productCollection = $this->_objectManager->create('Magento\Catalog\Model\ResourceModel\Product\Collection');
    $productCollection->addAttributeToFilter('visibility', 4);
    $productCollection->addAttributeToSelect('description');
    $productCollection->addAttributeToSelect('name');
    $productCollection->addCategoryIds();
    $productCollection->load();

This works absolutely fine for me... I'm not sure what getData is supossed to do. I just go throught it with:

    foreach ($productCollection as $item) {