How to get customer from observer in Magento 2?

Question

I need to send data to an external API when a customer (I mean a logged in customer) add a product to wishlist.

I found the event: wishlist_add_product.

$this->_eventManager->dispatch(
    'wishlist_add_product',
    ['wishlist' => $wishlist, 'product' => $product, 'item' => $result]
);

This event is not related to a customer, this is also triggered when a guest user add a product to wishlist.

In my Observer I have to check if the user is logged in, then I have to load some customer details and I can call the API.

The question is:

How do I get the customer ID if it is authenticated, when the customer object is not present in the dispatch?

app/code/Vendor/Module/etc/events.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="wishlist_add_product">
        <observer name="my_wishlist_add_product" instance="Vendor\Module\Observer\MyObserver" />
    </event>
</config>

app/code/Vendor/Module/Observer/MyObserver.php

<?php
namespace Vendor\Module\Observer;

use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;

class MyObserver implements ObserverInterface{
    public function execute(Observer $observer){
        // here I need something for load the logged in customer (if it is logged in)
    }
}

Answer 1

You can use and inject Magento\Customer\Model\Session in your observer class to get the logged in Customer Id. It doesn't matter whether the dispatched method has customer object, you can use this customer model session class to get the customer object.

Your observer should be like this

app/code/StackExchange/WishlistCustomer/Observer/WishlistAddItem.php

<?php
/**
 *   StackExchange_WishlistCustomer
 *   Jerome Dennis <[email protected]>
 */

namespace StackExchange\WishlistCustomer\Observer;

use Magento\Customer\Model\Session as CustomerSession;
use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;
use Magento\Framework\Message\ManagerInterface;
use Psr\Log\LoggerInterface;

/**
 * Class WishlistAddItem
 * @package StackExchange\WishlistCustomer\Observer
 */
class WishlistAddItem implements ObserverInterface
{

    /**
     * @var \Psr\Log\LoggerInterface
     */
    protected $logger;

    /**
     * @var \Magento\Customer\Model\Session
     */
    protected $customerSession;

    /**
     * @var \Magento\Framework\Message\ManagerInterface
     */
    protected $messageManager;

    /**
     * @param CustomerSession $customerSession
     * @param WishlistFactory $wishlistFactory
     * @param ManagerInterface $messageManager
     * @param \Psr\Log\LoggerInterface $logger 
     */
    public function __construct(
        CustomerSession $customerSession,
        ManagerInterface $messageManager,
        LoggerInterface $logger
    ) {
        $this->customerSession = $customerSession;
        $this->messageManager = $messageManager;
        $this->logger = $logger;
    }

    /**
     * @param Observer $observer
     * @return void
     * @SuppressWarnings(PHPMD.CyclomaticComplexity)
     */
    public function execute(Observer $observer)
    {
        $request = $observer->getEvent()->getRequest();
        // checks customer is logged in 
        if ($this->customerSession->isLoggedIn()) {
            // gets the logged in customer id from thje customer session model
            $customerId = $this->customerSession->getCustomerId();
            // customer id will be in debug.log
            $this->logger->info('Logged In Customer Id ('.__METHOD__.'): '.$customerId);
            //echo '<br/>$customerId : ' . $customerId;exit;
            return $this->customerSession->getCustomerId();
        }
    }
}

app/code/StackExchange/WishlistCustomer/etc/frontend/events.xml

<?xml version="1.0"?>
<!--
/**
 *   StackExchange_WishlistCustomer
 *   Jerome Dennis <[email protected]>
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="wishlist_add_item">
        <observer name="wishlist" instance="StackExchange\WishlistCustomer\Observer\WishlistAddItem" />
    </event>
</config>

app/code/StackExchange/WishlistCustomer/etc/module.xml

<?xml version="1.0"?>
<!--
/**
 *   StackExchange_WishlistCustomer
 *   Jerome Dennis <[email protected]>
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
    <module name="StackExchange_WishlistCustomer" setup_version="1.0.0">
        <sequence>
            <module name="Magento_Wishlist"/>
        </sequence>
    </module>
</config>

app/code/StackExchange/WishlistCustomer/registration.php

<?php
/**
 *   https://magento.stackexchange.com/questions/303499/how-to-get-customer-from-observer-in-magento-2
 * 
 *   StackExchange_WishlistCustomer
 *   Jerome Dennis <[email protected]>
 */

\Magento\Framework\Component\ComponentRegistrar::register(
    \Magento\Framework\Component\ComponentRegistrar::MODULE,
    'StackExchange_WishlistCustomer',
    __DIR__
);

Answer 2

Add This line in events.xml

<?xml version="1.0"?>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
   <event name="wishlist_add_item">
       <observer name="MyObserverName" instance="Vendor\Module\Observer\MyObserver" />
   </event>
</config>

this observer file run before this wishlist redirect to wishlist page.

In your MyObserver.php first check if customer is login or not and then your logic.

<?php

namespace Vendor\Module\Observer;

use Magento\Framework\Event\ObserverInterface;

class MyObserver implements ObserverInterface
{
    protected $customerSession;

    public function __construct(
        .................................................
        .................................................
        \Magento\Customer\Model\SessionFactory $customerSession,
        .................................................
        .................................................
    ) {
        .................................................
        .................................................
        $this->_customerSession = $customerSession->create();
        .................................................
        .................................................
    }

    public function execute(\Magento\Framework\Event\Observer $observer)
    {
        if ($this->_customerSession->isLoggedIn()) {
            $cusomerid =  $this->_customerSession->getId();
            print_r($cusomerid);
            exit();
        }
    }
}

I Hope This Helps You.