/**
* Finds the Listing model based on its primary key value.
* If the model is not found, a 404 HTTP exception will be thrown.
* @param integer $id
* @return Listing the loaded model
* @throws NotFoundHttpException if the model cannot be found
*/
protected function findModel($id)
{
if (($model = Listing::findOne($id)) !== null) {
return $model;
} else {
throw new NotFoundHttpException('The requested page does not exist.');
}
}