If you wounder how to create links in an extbase controller instead of using the old pi_getPageLink methode you should have a look at this:
$this->controllerContext->getUriBuilder()->reset()
->setArguments([
'tx_myext[action]'=>'show',
'tx_myext[param]'=>$model->getUid() ])
->setTargetPageUid($GLOBALS["TSFE"]->id)
->setCreateAbsoluteUri(true)
->buildFrontendUri();
To get more information you may search for getUriBuilder