Typo3 Call to a member function on null - dependency-injection

Question

I have seen similar problems on Stackoverflow but none of those answers has worked for me (including clearing cache, clearing PHP opcode cache systems, de-activating and re-activating the extension). Hopefully someone can point me in the right direction.
I am running a scheduled command for an extension. At some point my command will need to call the method test() from the MyController class.
I have tried to create a reference to the class via an inheritance call AND by ALL injection methods but no matter which way I try it I always get the same issue...:
Call to a member function test() on null
Most recently I used the injection method that is not recommended, but it simplifies my example below so I'll use it for now. (VendorName and ExtensionName are obvs dummy names):
* #var \VendorName\ExtensionName\Controller\MyController
* #inject
*/
protected $mc;
public function myCommand()
{
return $this->mc->test(); //should return true
}
...and inside MyController
public function test()
{
return true;
}

Answer 1

The issue isn't the injection call on the command Class, but some automatically generated code on the MyController Class. It seems Extension Builder can cause the error by incorrectly creating the #inject line in the wrong place. Here is the code it created automatically:
/**
* #var \VendorName\ExtensionKey\Domain\Repository\ExampleRepository
* #inject
*/
protected $importService = null;
/**
* #inject
*/
protected $exampleRepository = null;
...that second #inject call creates the error. It should be just:
/**
* #var \VendorName\ExtensionKey\Domain\Repository\ExampleRepository
* #inject
*/
protected $importService = null;
protected $exampleRepository = null;
Unfortunately the dubugging doesn't tell you which class is causing the issue so I naturally thought it was my own code.