What's the purpose of $this->get('Item') in Joomla view.html.php example file?

Question

I refer to the code below, presented in Developing a MVC Component - Front End Function Example:

class HelloWorldViewUpdHelloWorld extends JView
{
    // Overwriting JView display method
    function display($tpl = null) 
    {
            $app            = JFactory::getApplication();
            $params         = $app->getParams();
            $dispatcher = JDispatcher::getInstance();

            // Get some data from the models
            $state          = $this->get('State');
            $item           = $this->get('Item');  //WHAT IS THE PURPOSE OF THIS STATEMENT?
            $this->form     = $this->get('Form');

            // Check for errors.
            if (count($errors = $this->get('Errors'))) 
            {
                    JError::raiseError(500, implode('<br />', $errors));
                    return false;
            }
            // Display the view
            parent::display($tpl);
    }

}

I don't understand the purpose of this statement and I also notice that $item does not appear in the code in file site/views/updhelloworld/tmpl/default.php on that webpage.

I actually have the same question for the view.html.php file of com_users/views/registration of Joomla 3 code ( I thought by comparing the two form submit examples I could answer my question):

    $this->data     = $this->get('Data'); //WHAT IS THE PURPOSE OF THIS STATEMENT? WHAT PRECISELY KIND OF DATA iS MEANT HERE?
    $this->form     = $this->get('Form');
    $this->state    = $this->get('State');
    $this->params   = $this->state->get('params');

And also here $this->data does not appear in the related tmpl/default.php file (?)

Answer 1

In classes extending JView or JViewLegacy, a call to $this->get() will call a function in registered model classes starting with get. So calling $this->get('Item') will call a model's getItem method.

Answer 2

The $this->get('Item') calls the function getItem() in the model, and subsequently it loads the data from the database.

$this->get('Data') calls a method in the model that gets the registration form data and prepares it for use.

Have a look at getData in com_users/models/registration.php