Symfony custom many-to-many with checkbox - php

Question

Having Session, Person, Participant, I'm trying to create a Session, and a list with all Persons to check the participants.
The PersonInSession table keeps participants_ids and the session_id.
I'm getting the following Error:
Unable to transform value for property path "person": Expected a Doctrine\Common\Collections\Collection object.
I want to create a Session and directly check the participants in the same form.
PersonEntityType
class PersonEntityType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('name');
}
}
SessionEntityType
class SessionEntityType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('description')
->add('participant', CollectionType::class,
array(
'entry_type' => ParticipantEntityType::class,
'by_reference' => false,
'allow_add' => true,
'allow_delete' => true,
)
);
}
}
ParticipantEntityType
class ParticipantEntityType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('person', EntityType::class,
array(
'class' => 'AppBundle:PersonEntity',
'choice_label' => 'name',
'expanded' =>'true',
'multiple' => 'true'
)
);
}
}
PersonEntity
class PersonEntity
{
private $id;
private $name;
/**
* #ORM\OneToMany(targetEntity="ParticipantEntity", mappedBy="person")
*/
private $participant;
public function __construct()
{
$this->participant = new ArrayCollection();
}
}
SessionEntity
class SessionEntity
{
private $id;
private $description;
/**
* #ORM\OneToMany(targetEntity="ParticipantEntity", mappedBy="session")
*/
private $participant;
public function __construct()
{
$this->participant = new ArrayCollection();
}
}
ParticipantEntity
class ParticipantEntity
{
private $id;
/**
* #ORM\ManyToOne(targetEntity="PersonEntity", inversedBy="participant")
*/
private $person;
/**
* #ORM\ManyToOne(targetEntity="SessionEntity", inversedBy="participant")
*/
private $session;
public function __construct()
{
$this->person = new ArrayCollection();
}
}

Answer 1

You should have:
namespace AppBundle\Entity;
use Doctrine\Common\Collections\ArrayCollection
class ParticipantEntity
{
// ...
/**
* #var PersonEntity[]|ArrayCollection
*/
private $person;
public function __construct()
{
$this->person = new ArrayCollection();
}
// ...
Otherwise it cannot work as is.

Answer 2

in SessionEntityType, the participant field (you would better rename it to participants as that would be more meaningful) is a CollectionType field. So in its entry_type (ParticipantEntityType) you need to add a field which maps to a Collection property of the target Entity (ParticipantEntity).
In that entity you have person which has wrongly a ManyToOne relationship with your participant. So It should be defined as:
ParticipantEntity
class ParticipantEntity
{
/**
* #ORM\OneToMany(targetEntity="PersonEntity")
*/
private $persons;
public function __construct()
{
$this->person = new ArrayCollection();
}
}
I strongly recommend you to revise your entities, as they are clearly the source of problem.