Symfony2: The form's view data is expected to be an instance of entity but is array

Question

There are two actions (new and edit) that use the same form. The form shall create a new entity (MyBundle\Entity\Project) or edit an existing one. Each project can be assigned to one team (MyBundle\Entity\Team), one team can hold multiple projects.

Entity/Project.php:

/* ... */
/**
     * @var Team
     *
     * @ORM\ManyToOne(targetEntity="Team", inversedBy="projects")
     * @ORM\JoinColumn(name="team", referencedColumnName="id")
     */
    private $team;
/* ... */

Entity/Team.php:

/* ... */
/**
     * @var ArrayCollection
     *
     * @ORM\OneToMany(targetEntity="Project", mappedBy="team")
     * @ORM\OrderBy({"title" = "ASC"})
     **/
    private $projects;
/* ... */

Controller/ProjectController.php:

public function newAction()
    {
        $project = new Project();
        $form = $this->createForm(
            new new ProjectType($project),
            array(
                'action' => $this->generateUrl('mybundle_project_create'),
            )
        );

        /* ... */
    }

public function editAction($id, Request $request)
    {
        /** @var \Doctrine\ORM\EntityManager $em */
        $em = $this->getDoctrine()->getManager();
        $project = $em->getRepository('MyBundle:Project')->findOneById($id);

        $form = $this->createForm(
            new ProjectType($project),
            $project,
            array(
                'action' => $this->generateUrl('mybundle_project_edit', array('id' => $project->getId())),
            )
        );

Form/ProjectType.php:

private $project;

    public function __construct($project = null)
    {
        $this->project = $project;
    }

/**
     * @param FormBuilderInterface $builder
     * @param array $options
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            /* ... */
            ->add('team', 'entity', array(
                'class' => MyBundle:Team',
                'property' => 'name',
                'label' => 'Team',
                'query_builder' => function (TeamRepository $er) {
                    return $er->createQueryBuilder('e')
                        ->orderBy('e.name', 'ASC');
                },
                'expanded' => false,
                'multiple' => false,
                'required' => false
            ))
            ->add('save', 'submit');
    }

/**
     * @param OptionsResolverInterface $resolver
     */
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(
            array(
                'data_class' => 'MyBundle\Entity\Project',
            )
        );
    }

    /**
     * @return string
     */
    public function getName()
    {
        return 'mybundle_project';
    }

When I'm accessing the edit form, the dropdown shows the assigned team correctly. But when I'm trying to create a new project, it gives me the following error message:

The form's view data is expected to be an instance of class MyBundle\Entity\Project, but is a(n) array. You can avoid this error by setting the "data_class" option to null or by adding a view transformer that transforms a(n) array to an instance of MyBundle\Entity\Project.

Answer 1

ProjectController's newAction is calling the method createForm with 2 parameters instead of 3, it should be

$form = $this->createForm(
    new ProjectType($project),
    $project,
    array(
        'action' => $this->generateUrl('mybundle_project_create'),
    )
);

instead of

$form = $this->createForm(
    new ProjectType($this->getDoctrine()->getEntityManager(), $project),
    array(
        'action' => $this->generateUrl('mybundle_project_create'),
    )
);