Not able to disable block cache without affecting Magento FPC

Question

I have created a custom block where I am showing the number of items in the cart and also loggedin the customer name. I am getting correct count and customer name on checkout page.But not on any other pages such as Product page, home page etc. This is because I have enabled full page caching. If I disable FPC then everything works fine. But I want to keep FPC and also need to show this count on other pages. How it can be done? I have already tried many codes like $this->_isScopePrivate = true; in constructor. But it's not working. I am using Magento 2.3.1. Below is sample code:

class ShoppingCart extends \Magento\Framework\View\Element\Template
{
    public function __construct(
        \Magento\Framework\View\Element\Template\Context $context,
        \Magento\Checkout\Model\Session $checkoutSession,
        array $data = []
    ) {
        $this->_checkoutSession = $checkoutSession;;
        parent::__construct($context, $data);
        $this->_isScopePrivate = true;

    }



    /**
     * Get quote object associated with cart. By default it is current customer session quote
     *
     * @return \Magento\Quote\Model\Quote
     */
    public function getQuoteData()
    {
        $this->_checkoutSession->getQuote();
        if (!$this->hasData('quote')) {
            $this->setData('quote', $this->_checkoutSession->getQuote());
        }
        return $this->_getData('quote');
    }

    public function getMyCustomMethod(){
        return "test function callecd";
    }
}

and calling in logo.phtml page as.

$blockObj= $block->getLayout()->createBlock('Rbj\Customer\Block\ShoppingCart');
$quote =  $blockObj->getQuoteData();
$itemsCount = $quote->getItemsCount();
$itemsCount = $blockObj->getMyCustomMethod();

Please advice. Thanks in advance.

Answer 1

Magento 2 has special system for display personal/private customer data on the cachable pages.

Shortly: magento use additional ajax query to retrieve all needed private data (including data you needed). Than you can use this data from js.

Private content in magento

In the Luma theme the minicart works using this way.

Here is additional query to private data:

http://prntscr.com/o7iwx4

Here is layout for minicart:
vendor/magento/module-checkout/view/frontend/layout/default.xml

Block
Magento\Checkout\Block\Cart\Sidebar
has inside js-layout which conteins js-components.

You can find them in vendor/magento/module-checkout/view/frontend/web