how to save one-to-many relationships to the database using zend form and doctrine - database

Question

I'm writing an application that uses Zend Framework 2 and Doctrine (both the latest stable version).
There is much documenation (mainly tutorials and blog posts) that deal with saving doctrine entities to the database in combination with Zend Form. Unfortunately they only deal with simple entities that do not have one-to-many or many-to-many relationships.
This is one of those examples that i have adopted into my own code.
http://www.jasongrimes.org/2012/01/using-doctrine-2-in-zend-framework-2/
I understand that in the Album Entity of this example, the artist is a string to keep the (already lengthy) tutorial as simple as possible. But in a real world situation this would of course be a one-to-many releationship with an Artist Entity (or even a many-to-many). In the view, a select-box could be displayed where the artist can be selected, listing all the artist-entities that could be found in the database, so the right one can be selected.
Following the example with the album, this is how i've set up an 'edit' Action in my controller:
public function editAction()
{
// determine the id of the album we're editing
$id = $this->params()->fromRoute("id", false);
$request = $this->getRequest();
// load and set up form
$form = new AlbumForm();
$form->prepareElements();
$form->get("submit")->setAttribute("label", "Edit");
// retrieve album from the service layer
$album = $this->getSl()->get("Application\Service\AlbumService")->findOneByAlbumId($id);
$form->setBindOnValidate(false);
$form->bind($album);
if ($request->isPost()) {
$form->setData($request->getPost());
if ($form->isValid()) {
// bind formvalues to entity and save it
$form->bindValues();
$this->getEm()->flush();
// redirect to album
return $this->redirect()->toRoute("index/album/view", array("id"=>$id));
}
}
$data = array(
"album" => $album,
"form" => $form
);
return new ViewModel($data);
}
How would this example need to be altered if the artist wasn't a string, but an Artist Entity?
And suppose the album also has multiple Track Entities, how would those be processed?

Answer 1

The example would not need to be changed at all, the changes will happen with your entity and your form.
This is a good reference: Doctrine Orm Mapping
So to save yourself a lot of extra work, your OnToMany relationship would use: cascade = persist:
/**
* #ORM\OneToMany(targetEntity="Artist" , mappedBy="album" , cascade={"persist"})
*/
private $artist;
When it comes to persisting the form object, the entity knows it must save the associated entity as well. If you did not include this, then you would have to do it manually using a collection.
To make like easier with your form, you can use Doctrines Object Select like this:
$this->add(
[
'type' => 'DoctrineModule\Form\Element\ObjectSelect',
'name' => 'artist',
'options' => [
'object_manager' => $this->objectManager,
'target_class' => 'Artist\Entity\Artist',
'property' => 'name', //the name field in Artist, can be any field
'label' => 'Artist',
'instructions' => 'Artists connected to this album'
],
'attributes' => [
'class' => '', //Add any classes you want in your form here
'multiple' => true, //You can select more than one artist
'required' => 'required',
]
]
);
So now your form takes care of the collection for you, the controller as per your example does not need to change since the entity will take care of the persisting...
Hope this gets you on track.