小编Den*_*est的帖子

我必须序列化一个对象，我得到了如此常见的“循环引用错误”

我使用了旧的 Symfony 方法：

$normalizer = new ObjectNormalizer();
// Add Circular reference handler
$normalizer->setCircularReferenceHandler(function ($object) {
    return $object->getId();
});
$normalizers = array($normalizer);
$encoders = [new JsonEncoder()];
$serializer = new Serializer($normalizers, $encoders);

这项工作但从 Symfony 4.2 开始，我得到了您在此问题标题中看到的异常：

使用上下文的“circular_reference_handler”键代替 Symfony 4.2

我在有关序列化程序的 Symfony 文档中找不到对此的任何参考。

https://symfony.com/doc/current/components/serializer.html#handling-circular-references

有谁知道如何使用这个“上下文键”而不是旧方法？

我的 Symfony 4.2.6 应用程序中有一个 ManyToMany 关系，我希望它可以为空。

所以我的第一个实体 SpecialOffers 如下：

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

/**
 * @ORM\Entity(repositoryClass="App\Repository\SpecialOfferRepository")
 */
class SpecialOffer
{
    /**
     * @ORM\ManyToMany(targetEntity="App\Entity\Neighbourhood", inversedBy="specialOffers")
     */
     private $neighbourhood;

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

    /**
     * @return Collection|Neighbourhood[]
     */
    public function getNeighbourhood(): Collection
    {
        return $this->neighbourhood;
    }

    public function addNeighbourhood(Neighbourhood $neighbourhood): self
    {
        if (!$this->neighbourhood->contains($neighbourhood)) {
            $this->neighbourhood[] = $neighbourhood;
        }

        return $this;
    }

    public function removeNeighbourhood(Neighbourhood $neighbourhood): self
    {
        if ($this->neighbourhood->contains($neighbourhood)) {
            $this->neighbourhood->removeElement($neighbourhood);
       } …