Need Some more Clarification about - Initialisation of Class from Constructor and Di.xml in Magento2

Question

• i need to initialise the class from di.xml way(replace constructor)

• <type name="Test\ContactUs\Plugin\Controller\Index\Post"> <arguments> <argument name="contactUsCheck" xsi:type="object">Test\ContactUs\Model\ContactUs</argument></arguments></type>

• here I am trying to inject ContactUs Class from di.xml(argument) way. instead of directly injecting from - Constructor

• it is not working I already define the argument name="contactUsCheck" in the constructor

  public function __construct(
   Context $context,
   ConfigInterface $contactsConfig,
   MailInterface $mail,
   DataPersistorInterface $dataPersistor,
   LoggerInterface $logger = null,
   ContactusRepositoryInterface $contactusRepository,
   $contactUsCheck
  

  ) { parent::__construct($context, $contactsConfig, $mail, $dataPersistor, $logger); $this->dataPersistor = $dataPersistor; $this->logger = $logger; $this->mail = $mail; $this->contactusRepository = $contactusRepository; $this->contactUsCheck = $contactUsCheck; }

• Need some explanation why it is not working