How is the order attached to newly created customer after checkout

Question

Hey I hope this question isn't to broad but how is the order attached to a customer that is created after guest checkout?

Background to my question:
I want to attach a custom field to my customer. This custom field is acquired in checkout and stored in the order. I tried to receive the order in a observer watching the customer_register_success event:

namespace Vendor\CheckoutCustomerInfo\Observer;


use Magento\Customer\Model\Customer;
use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;
use Magento\Sales\Model\ResourceModel\Order\CollectionFactoryInterface;

class AddInfoFromOrderToCustomerObserver implements ObserverInterface
{

    private $collectionFactoryInterface;

    public function __construct(CollectionFactoryInterface $collectionFactoryInterface)
    {
        $this->collectionFactoryInterface = $collectionFactoryInterface;
    }

    /**
     * @param Observer $observer
     *
     * @return void
     */
    public function execute(Observer $observer)
    {
        /**
         * @var Customer $customer
         */
        $customer = $observer->getCustomer();

        $orders = $this->collectionFactoryInterface->create($customer->getId())->addFieldToSelect(
            '*'
        )->setOrder(
            'created_at',
            'desc'
        );
    }
}

But in $orders I do not have the order.

Am I doing something wrong with querying the orders of the customer or is it attached somehow different? Is this event to early to get the order?

Thanks in advance!

Answer 1

After a bit more debugging I figured out the orders are lazy loaded. I need to call $orders->getItems() or $orders->getFirstItem()in order to have them actually loaded.