What's the purpose of $this->get('Item') in view.html.php? - Joomla! Forum - community, help and support

i refer code below in http://docs.joomla.org/j2.5:developing_ ... e_function:

code: select all

class helloworldviewupdhelloworld extends jview
{
    // overwriting jview display method
    function display($tpl = null)
    {
            $app            = jfactory::getapplication();
            $params         = $app->getparams();
            $dispatcher = jdispatcher::getinstance();

            // data models
            $state          = $this->get('state');
            $item           = $this->get('item');  //what purpose of statement?
            $this->form     = $this->get('form');

            // check errors.
            if (count($errors = $this->get('errors')))
            {
                    jerror::raiseerror(500, implode('<br />', $errors));
                    return false;
            }
            // display view
            parent::display($tpl);
    }
}

i don't understand purpose of statement , notice $item not appear in code in file site/views/updhelloworld/tmpl/default.php on webpage.

i have same question view.html.php file of com_users/views/registration of joomla 3 code ( thought comparing 2 form submit examples answer question):

code: select all

$this->data     = $this->get('data'); //what purpose of statement? precisely kind of data meant here?
    $this->form     = $this->get('form');
    $this->state    = $this->get('state');
    $this->params   = $this->state->get('params');

and here $this->data not appear in related tmpl/default.php file (?)

$item = $this->get('item'); //what purpose of statement?

this refers getitem() method in model. please note warning @ top of tutorial methods not adhering best practices.

$this->data = $this->get('data'); //what purpose of statement? precisely kind of data meant here?

it gets registration form data using method getdata() model