How do we know which factories class need to use in Magento2?

Question

This is the code I copied from MagePlaza.

class Index extends \Magento\Framework\App\Action\Action
{
    protected $_pageFactory;

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

    public function execute()
    {
        return $this->_pageFactory->create();
    }
}

How we will decide that here we need to use PageFactory and why we pass Magento\Framework\App\Action\Context in the constructor.

Can anyone help me out this please?

Answer 1

Factories are used everywhere where you need one or multiple instances of same Class.

If you use class itself to load your specific object instead, it will act like Singleton, so it will be same instance on every occurrences of that class object not constructed with Factory.

The Context is used to tell Magento in which context you are in. For example if you want to get some request data or use registry to load or save some data, you will need to take Context in mind, because data could be different in different places.