Magento 2 Dependency Injection

Dependency Injection (DI) is a design pattern used in Magento 2 to manage class dependencies. Instead of creating objects manually using new or ObjectManager, Magento automatically injects required objects through the constructor.

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💡 Why Magento Uses Dependency Injection

• 🧪 Makes code testable
• 🔁 Supports automatic class reuse
• 🔐 Improves security and maintainability
• ⚙️ Controls object creation from a single place (DI Container)

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📦 Constructor Injection Example

Magento 2 injects dependencies via class constructors.

<?php
namespace Vendor\Module\Model;

use Magento\Catalog\Api\ProductRepositoryInterface;

class Example
{
    protected $productRepository;

    public function __construct(ProductRepositoryInterface $productRepository)
    {
        $this->productRepository = $productRepository;
    }

    public function getProductById($id)
    {
        return $this->productRepository->getById($id);
    }
}
  

✅ Magento automatically creates and injects the `ProductRepositoryInterface` object.

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⚙️ Configuration via `di.xml` (If Needed)

You can customize DI behavior using `di.xml`.

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🚫 Avoid Using ObjectManager Directly

❌ Don’t do this:

$objectManager = \Magento\Framework\App\ObjectManager::getInstance();
$productRepo = $objectManager->get('Magento\Catalog\Api\ProductRepositoryInterface');
  

✅ Use DI instead (it’s cleaner and testable).

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🔁 Constructor Injection vs Factory Injection

| Method | When to Use |
|———————-|————————————-|
| Constructor Injection | For required dependencies |
| Factory Injection | For dynamic, optional, or new objects |

Example for Factory:

use Magento\Catalog\Model\ProductFactory;

public function __construct(ProductFactory $productFactory)
{
    $this->productFactory = $productFactory;
}

public function createProduct()
{
    return $this->productFactory->create();
}
  

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📌 Best Practices

• ✔️ Always prefer constructor injection
• 🧪 Use interfaces (e.g., `ProductRepositoryInterface`)
• 🧼 Avoid using ObjectManager directly
• 🔧 Use `di.xml` only for customizations

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🧠 Memory Tip: C-FAB

Remember **C-FAB** for DI patterns:

– **C**onstructor injection (most used)
– **F**actory for dynamic objects
– **A**void ObjectManager
– **B**ind interfaces in `di.xml`

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✅ Summary

• Magento 2 uses Dependency Injection to manage class dependencies
• DI improves testability and reduces tight coupling
• Always use constructor injection with interfaces