We can use the following code snippet to check whether the customer is logged in or not in Magento2 with the help of customer session model class object.


use Magento\Customer\Model\Session;

$protected customerSession;

/**
 * Class constructor.
 * @param Session $customerSession
 */
public function __construct(
    Session $customerSession    
)
{
    $this->customerSession = $customerSession;    
}

/**
 * check whether customer is logged in or not
 *
 * @return bool
 */
public function isCustomerLoggedIn()
{
    $this->customerSession->isLoggedIn() ? true : false;
}