Block with PHP methods only - preferable inheritance

Question

I often create blocks containing PHP methods, not binded with any template by design. They are sometimes used only in one place, sometimes throughout an app. So far, I was making them inherit from \Magento\Framework\View\Element\Template, but I am not sure if it is the best way. Maybe there is some other abstract block class most suitable for such a 'php-only' blocks?

example - this one is used on product pages in order to check if provided product is in cart already (it has no template assigned):

namespace [Vendor]\[ModuleName]\Block\Catalog\Product;

use \Magento\Catalog\Api\Data\ProductInterface;
use \Magento\Checkout\Model\Session;
use \Magento\Framework\View\Element\Template;
use \Magento\Framework\View\Element\Template\Context;

class IsInCart extends Template
{

private $checkoutSession;

public function __construct(
    Session $checkoutSession,
    Context $context,
    array $data  = []
)
{
    parent::__construct($context, $data);

    $this->checkoutSession = $checkoutSession;
}

public function isInCart(ProductInterface $product)
{
    $productId = $product->getId();
    $cartItems = $this->checkoutSession->getQuote()->getAllVisibleItems();
    $itemsIds = array();
    foreach ($cartItems as $cartItem) {
        $itemsIds[] = $cartItem->getProduct()->getId();
    }

    return in_array($productId, $itemsIds);
}


public function countItemsInCart()
{
    $cartItems = $this->checkoutSession->getQuote()->getAllVisibleItems();
    $cartItemsCount = count($cartItems);

    return $cartItemsCount;
}

Answer 1

The right block to extend in the case of a block that does not render anything is Magento\Framework\View\Element\AbstractBlock. However, blocks that do not render anything are somewhat useless, and you would probably be better served to move that functionality into another block, or a model or helper file.