Why can't I inject the ProductRepositoryInterface in Magento 2?

Question

I have a controller action into which I would like to inject the product-repository

namespace Nosto\Tagging\Controller\Export;

use Magento\Catalog\Api\ProductRepositoryInterface;
use Magento\Store\Model\StoreManagerInterface;
use Magento\Backend\App\Action;
use Magento\Framework\App\Action\Context;

class Test extends Action
{

    private $_productRepository;

    public function __construct(
        Context $context,
        StoreManagerInterface $storeManager,
        ProductRepositoryInterface $productRepository    
    ) {
        parent::__construct($context);
        $this->_storeManager = $storeManager;
        $this->_productRepository = $productRepository;
    }

No matter what order I put my constructor arguments, Magento's dependency-injection always injects an invalid class for the productRepository argument leading PHP to throw and argument error. The storeManager getd injected just fine. Clearing the caches haven't helped.

Here is the exception thrown:

Recoverable Error: Argument 3 passed to Nosto\Tagging\Controller\Export\Test::__construct() must implement interface Magento\Catalog\Api\ProductRepositoryInterface, instance of Nosto\Tagging\Helper\Account given.

The class names and argument positions in the error message change but the error definition is always the same. Removing the ProductRepositoryInterface from the constructor makes everything fine again.

Answer 1

This generally crops up when you add another parameter to the constructor because Magento caches it in var/generation. You need to clear var/generation which forces Magento to regenerate the interceptor.

Answer 2

It's hard to say without further details, but I'm going to assume youe code sample actually looks something like this

namespace Packagename\Module\Controller;
class Test extends Action
{

    private $_productRepository;

    public function __construct(
        Context $context,
        StoreManagerInterface $storeManager,
        ProductRepositoryInterface $productRepository    
    ) {
        parent::__construct($context);
        $this->_storeManager = $storeManager;
        $this->_productRepository = $productRepository;
    }
}

i.e. with a PHP namespace (since all controllers have namespaces in Magento 2).

If that's the case, then in your code sample you're actually trying to inject a Packagename\Module\Controller\ProductRepositoryInterface class. If you use a class name without a namespace prefix, PHP assumes you want a class in the current namespace.

Answer 3

I was not able to inject any module to a controller with this error message. Deleting var/generation worked for me..

Answer 4

What worked for me is running the compile command.

/var/www/magento2-root$ php bin/magento setup:di:compile

Answer 5

In magento 2.2 delete folder:

"generated/code"

And that will solve the problem.