Introduction to Magento 2 Object Manager

Object-oriented programming started in PHP 5 but has some restrictions compared to other languages. In Magento 1, the Mage class was used to handle most objects. In Magento 2, Object Manager replaces Mage, fixing issues by connecting three patterns: managing objects, injecting dependencies, and using plugins. Object Manager is a PHP class that helps make and find objects in Magento 2. It is also in charge of making types of objects called factories and proxies.

Object Manager Mechanism

To obtain the Magento 2 Object Manager instance ( for example, getting the object manager in phtml), you can use the following code:

<?php
$objectManager = \Magento\Framework\App\ObjectManager::getInstance();

To get the object Manager in the constructor: 
/
    * @var \Magento\Framework\ObjectManagerInterface
    */
   private $objectManager;

   /
    * @param \Magento\Framework\ObjectManagerInterface $objectmanager
    */
   public function __construct(
       \Magento\Framework\ObjectManagerInterface $objectmanager
   ) {
       $this->objectManager = $objectmanager;
   }

With the Object Manager, you can either obtain a single instance of a PHP class (using the “get” method) or generate a new one (using the “create” method).

For example:

<?php
$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
/* Create a new product object */
$product = $objectManager->create(\Magento\Catalog\Model\Product::class);
/* Get a request object singleton
$request = $objectManager->get(\Magento\Framework\App\RequestInterface::class);

Object Manager Configuration

The di.xml file sets up the object manager and instructs it on managing dependency injection.

It shows the desired class implementation that the object manager should use for interfaces declared in constructors.

Additionally, it determines whether the object manager should generate a new object for each request or if it should treat the object as a singleton.

Exceptions in Object Manager

It’s essential to refrain from directly employing the ObjectManager in your code, as shown in the previous example, as it hides the actual dependencies of the class.

You can use the Object Manager in the following scenarios:

• When testing your code.
• Depending on classes used to create objects like factories or proxies classes.
• To maintain backward compatibility adjustments in the PHP class constructor.
• In static magic methods, such as __wakeup(), __sleep(), etc.

Object Manager in Use

Examples showing the use of Object Manager for various Magento development tasks:

✔ How to get Customer Collection in Magento 2

✔ How to Get the data of shopping cart items, subtotal, grand total, billing & shipping address in Magento 2

✔ Create helper class

✔ Magento 2 create product programmatically