php - Zend Framework 2: setAttribute() on a non-object error occurs when trying to edit -

i'm new php zend framework 2 , i'm going through 1 of online tutorials in learning how use it. tutorial involves having create , edit albums. problem when try edit album clicking on edit links, error stating:

call member function setattribute() on non-object

controller:

public function editaction()  {      $id = (int) $this->params()->fromroute('id', 0);      if (!$id) {          return $this->redirect()->toroute('album', array(              'action' => 'add'          ));      }       // album specified id.  exception thrown      // if cannot found, in case go index page.      try {          $album = $this->getalbumtable()->getalbum($id);      }      catch (\exception $ex) {          return $this->redirect()->toroute('album', array(              'action' => 'index'          ));      }       $form = new albumform();      $form->bind($album);      $form->get('submit')->setattribute('value', 'edit');       $request = $this->getrequest();      if ($request->ispost()) {          $form->setinputfilter($album->getinputfilter());          $form->setdata($request->getpost());           if ($form->isvalid()) {              $this->getalbumtable()->savealbum($album);               // redirect list of albums              return $this->redirect()->toroute('album');          }     // edit: bracket below missing     // causing 'setattribute' error when     // clicking on edit links of albums      }       return array(          'id' => $id,          'form' => $form,      );  } 

view:

<?php //module/album/view/album/album/edit.phtml:  $title = 'edit album'; $this->headtitle($title); ?>  <h1><?php echo $this->escapehtml($title); ?> </h1>  <?php $form = $this->form; $form->setattribute('action', $this->url( 'album', array(     'action' => 'edit',     'id'     => $this->id,     ) )); $form->prepare();  echo $this->form()->opentag($form); echo $this->formhidden($form->get('id')); echo $this->formrow($form->get('title')); echo $this->formrow($form->get('artist')); echo $this->formsubmit($form->get('submit')); echo $this->form()->closetag();  ?>     

edit: here code albumform.php

albumform.php:

<?php  namespace album\form;  use zend\form\form;  class albumform extends form {    public function __construct($name = null)    {     // want ignore name passed     parent::__construct('album');      $this->add(array(         'name' => 'id',         'type' => 'hidden',         ));     $this->add(array(         'name' => 'title',         'type' => 'text',         'options' => array(             'label' => 'title',         ),         ));     $this->add(array(         'name' => 'artist',         'type' => 'text',         'options' => array(             'label' => 'artist',             ),         ));     $this->add(array(         'name' => 'submit',         'type' => 'submit',         'attributes' => array(             'value' => 'go',             'id' => 'submitbutton',             ),         ));    } }  ?> 

i'm not sure why occurring since i'm following tutorial exactly, appreciated!