Error on "simple" CollectionType inclusion - php

Question

I try to make a form for an entity called Product with an embedded form from an entity Barcode. When I try to go to the form to add one product, I have the message "Return value of App\Entity\Product::getBarcodes() must implement interface Doctrine\Common\Collections\Collection, null returned".
I say in __construct to initialize the barcodes to implement the Collection but still the same..
My Barcode Entity
<?php
namespace App\Entity;
use Doctrine\ORM\Mapping as ORM;
/**
* #ORM\Entity(repositoryClass="App\Repository\BarcodeRepository")
*/
class Barcode
{
/**
* #ORM\Id()
* #ORM\GeneratedValue()
* #ORM\Column(type="integer")
*/
private $id;
/**
* #ORM\Column(type="string", length=255)
*/
private $code;
/**
* #ORM\ManyToOne(targetEntity="App\Entity\Product", inversedBy="barcodes")
* #ORM\JoinColumn(nullable=false)
*/
private $product;
public function __construct(Product $product = null)
{
$this->product = $product;
}
public function getId(): ?int
{
return $this->id;
}
public function getCode(): ?string
{
return $this->code;
}
public function setCode(string $code): self
{
$this->code = $code;
return $this;
}
public function getProduct(): ?Product
{
return $this->product;
}
public function setProduct(?Product $product): self
{
$this->product = $product;
return $this;
}
}
My Product Entity :
<?php
namespace App\Entity;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Validator\Constraints as Assert;
use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
/**
* #ORM\Entity()
* #ORM\InheritanceType("JOINED")
* #ORM\DiscriminatorColumn(name="type", type="string")
* #UniqueEntity("slug")
*/
class Product
{
/**
* #ORM\Id()
* #ORM\GeneratedValue()
* #ORM\Column(type="integer")
*/
protected $id;
/**
* #ORM\Column(type="string", length=255)
*/
protected $name;
/**
* #ORM\Column(type="string", length=255)
* #Assert\Regex(pattern="/\.(svg|png)$/")
*/
protected $picture;
/**
* #ORM\Column(type="boolean")
*/
protected $is_activated;
/**
* #ORM\Column(type="string", length=255, nullable=true)
*/
protected $comments;
/**
* #ORM\Column(type="datetime")
*/
protected $created_at;
/**
* #ORM\OneToMany(targetEntity="App\Entity\Barcode", mappedBy="product", orphanRemoval=true, cascade={"all"})
*/
protected $barcodes;
public function __construct()
{
$this->allergens = new ArrayCollection();
$this->barcodes = new ArrayCollection();
}
public function getId(): ?int
{
return $this->id;
}
public function getName(): ?string
{
return $this->name;
}
public function setName(string $name): self
{
$this->name = $name;
return $this;
}
public function getPicture(): ?string
{
return $this->picture;
}
public function setPicture(string $picture): self
{
$this->picture = $picture;
return $this;
}
public function getIsActivated(): ?bool
{
return $this->is_activated;
}
public function setIsActivated(bool $is_activated): self
{
$this->is_activated = $is_activated;
return $this;
}
public function getComments(): ?string
{
return $this->comments;
}
public function setComments(?string $comments): self
{
$this->comments = $comments;
return $this;
}
public function getCreatedAt(): ?\DateTimeInterface
{
return $this->created_at;
}
public function setCreatedAt(\DateTimeInterface $created_at): self
{
$this->created_at = $created_at;
return $this;
}
/**
* #return Collection|Barcode[]
*/
public function getBarcodes(): Collection
{
return $this->barcodes;
}
public function addBarcode(Barcode $barcode): self
{
if (!$this->barcodes->contains($barcode)) {
$this->barcodes[] = $barcode;
$barcode->setProduct($this);
}
return $this;
}
public function removeBarcode(Barcode $barcode): self
{
if ($this->barcodes->contains($barcode)) {
$this->barcodes->removeElement($barcode);
// set the owning side to null (unless already changed)
if ($barcode->getProduct() === $this) {
$barcode->setProduct(null);
}
}
return $this;
}
}
and my ProductType:
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('name')
->add('slug')
->add('picture')
->add('barcodes', CollectionType::class, [
'entry_type' => BarcodeType::class,
'allow_add' => true,
'allow_delete' => true,
'prototype' => true,
'by_reference' => false
])
->add('is_activated')
->add('comments')
;
}

Answer 1

In your Product entity, allow the possibility of a null return type by changing Collection to ?Collection:
/**
* #return Collection|Barcode[]|null
*/
public function getBarcodes(): ?Collection
{
return $this->barcodes;
}