Magento2 - how to know when what parameter i have to pass in controller - _construct function

Question

i was reading a book magento2 tutorial. When learning how to create module. 2 augments was receiving in _construct function of controller.

Actually i am talking about this 2

\Magento\Framework\App\Action\Context $context,
\Magento\Framework\View\Result\PageFactory $resultPageFactory

how to know when which augment i have to use? i.e when working with product, order, customer. for example i saw that in other tutorial for get product list i have to use some like productfactory

Below is complete code for that controller

public function __construct(
\Magento\Framework\App\Action\Context $context,
\Magento\Framework\View\Result\PageFactory $resultPageFactory
) {
$this->resultPageFactory = $resultPageFactory;
parent::__construct($context);
}

Answer 1

You have to use RequestInterface

public function __construct(
  \Magento\Framework\App\Action\Context $context,
  \Magento\Framework\View\Result\PageFactory $resultPageFactory,
  \Magento\Framework\App\RequestInterface $request
) {
    $this->resultPageFactory = $resultPageFactory;
    $this->request = $request;
    parent::__construct($context);
}

public function execute(){
       $value = $this->request->getParam('yourkey');
}

Your ajax call is like:

$.ajax({
      url: {Yourcontrollerurl},
      data: {yourkey: $('#yourHtmlTagID').val()},
      type: 'post',
      ---
      });

don't forgot to recompile.

Answer 2

You can use

\Magento\Framework\App\RequestInterface $request

or can use

$this->getRequest()->getParam('Your Variable Name')

or

use Magento\Framework\App\Request\DataPersistorInterface;

$post = $this->getRequest()->getPostValue();
var_dump($post);