Symfony2: class 'Doctrine\Common\Collections\ArrayCollection' was not found in the chain configured namespaces

Question

Error occurs when attempting to persist a one-to-many relationship. In particular, a client may have multiple household members; a given household member is associated with one and only one client. [I am new to Symfony so errors are expected!] Your guidance gratefully accepted.

N.B. Alternate controller snippet below yields integrity constraint error by trying to set the client's id in the household table to null.

Clients Entity snippet

namespace Mana\AdminBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\ArrayCollection;

/**
 * Mana\AdminBundle\Entity\Clients
 *
 * @ORM\Table(name="clients")
 * @ORM\Entity
 */
class Clients
{
    protected $members;

    public function __construct()
    {
        $this->members = new ArrayCollection();
    }

    public function getMembers()
    {
        return $this->members;
    }

    public function setMembers(ArrayCollection $members)
    {
        $this->members = $members;
    }

    /**
     * @var integer $id
     *
     * @ORM\Column(name="id", type="integer", nullable=false)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     * @ORM\OneToMany(targetEntity="Household", mappedBy="clients")
     * @ORM\ManyToOne(targetEntity="EthDesc", inversedBy="clients")
     * @ORM\JoinColumn(name="eid", referencedColumnName="id")
     */

Household Entity snippet

namespace Mana\AdminBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * Mana\AdminBundle\Entity\Household
 *
 * @ORM\Table(name="household")
 * @ORM\Entity(repositoryClass="Mana\AdminBundle\Entity\HouseholdRepository")
 */
class Household {

    /**
     * @var integer $hid
     *
     * @ORM\Column(name="hid", type="integer", nullable=false)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     * @ORM\ManyToOne(targetEntity="Clients", inversedBy="members")
     * @ORM\JoinColumn(name="cid", referencedColumnName="id")
     * @ORM\ManyToOne(targetEntity="EthDesc", inversedBy="members")
     * @ORM\JoinColumn(name="eid", referencedColumnName="id")
     */

ClientsType snippet

    ->add('members', 'collection', array(
        'type' => new HouseholdType(),
        'allow_add' => true, 
        'by_reference' => false,
        'cascade_validation'  => true,
        ));

Controller snippet

public function createAction(Request $request) {
    $entity = new Clients();
    $form = $this->createForm(new ClientsType(), $entity);
    $form->bind($request);

    if ($form->isValid()) {
        $em = $this->getDoctrine()->getManager();
        $em->persist($entity);
        $em->persist($entity->getMembers());
        $em->flush();
        return $this->redirect($this->generateUrl('clients_show', array('id' => $entity->getId())));
    }
}

Alternate controller snippet

public function createAction(Request $request) {
    $entity = new Clients();
    $form = $this->createForm(new ClientsType(), $entity);
    $form->bind($request);

    if ($form->isValid()) {
        $em = $this->getDoctrine()->getManager();
        $em->persist($entity);
        foreach ($entity->getMembers() as $member)
        {
            $em->persist($member);
        }
        $em->flush();
        return $this->redirect($this->generateUrl('clients_show', array('id' => $entity->getId())));
    }

Answer 1

The times I have gotten this to work, I did not

use Doctrine\Common\Collections\ArrayCollection; 

I just

$this->field = new \Doctrine\Common\Collections\ArrayCollection();

in my constructor.

Also, you may want to consider adding Household (which appear to be the members in clients) as an entity form:

->add('members', 'entity', array(
    'type' => new HouseholdType(),
    'allow_add' => true, 
    'by_reference' => false,
    ));