Learn how to fix the Fatal error: Cannot instantiate interface in Magento 2. Our Magento Support team is here to help you with your questions and concerns.

Fixing Magento 2 ‘Cannot Instantiate Interface’ Errors

Did you run into an error while trying to run a CLI command in Magento after an upgrade?

Fear not! Our experts are here to help you out. The error message typically looks like this:

Cannot instantiate interface Klevu\Search\Api\Service\Catalog\Product\StockServiceInterface#0 /var/www/html/vendor/magento/framework/ObjectManager/ObjectManager.php(70): Magento\Framework\ObjectManager\Factory\Dynamic\Developer->create(‘Klevu\\Search\\Ap…’)
#1 /var/www/html/vendor/klevu/module-productsearch/Helper/Stock.php(29): Magento\Framework\ObjectManager\ObjectManager->get(‘Klevu\\Search\\Ap…’)

How to Fix the Post-Upgrade Issue

To resolve this issue and successfully run Magento commands, we need to flush all Redis sessions.

• Flush the Redis Cache:

  Run the command to flush the Redis cache.
  warden redis flushall

  This will result in ‘OK’ as the output.
• Run Magento Commands:

  After the Redis cache is flushed, we can run any Magento command, such as:

  php bin/magento cache:flush
php bin/magento setup:upgrade
php bin/magento setup:di:compile

Common Causes of the Error

• The `di.xml` file may lack the necessary mapping between the interface and its concrete implementation.
• The `di.xml` file may have incorrect mappings, causing Magento to attempt to instantiate an interface directly.
• Furthermore, outdated or corrupted code generation can lead to dependency resolution failures in Magento.

Troubleshooting Tips

• Enabling debug mode offers more detailed error messages in the Magento logs. This will help find the problematic configuration.
• Verify that the `di.xml` file correctly maps interfaces to their implementations. This file is located in the `etc` directory of a module.

  For example:

  If we have an interface `Vendor\Module\Api\MyInterface` and a class `Vendor\Module\Model\MyClass` implementing this interface, configure the DI container to map the interface to the implementation.

  
• Also, make sure the class constructors correctly declare their dependencies.

  For example:

  
• Next, clear and regenerate Magento’s generated code.

  php bin/magento setup:di:compile
php bin/magento cache:clean
php bin/magento cache:flush
• We need to make sure no conflicting modules override or interfere with the dependency injection configurations.
• Also, look for conflicting preferences in `di.xml` files across different modules.
• Furthermore, make sure there are no duplicate or conflicting class definitions.

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Conclusion

In brief, our Support Experts demonstrated how to fix the Fatal error: Cannot instantiate interface in Magento 2