Update One-To-Many relation using sonata_type_collection in Sonata Admin Bundle

gistfile1.txt

/**
 * @ORM\Entity
 * @ORM\Table(name="resident_log_translations")
 */
class ResidentLogTranslation
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\ManyToOne(targetEntity="Plusquam\Bundle\ContractBundle\Entity\ResidentLog", inversedBy="translations")
     * @ORM\JoinColumn(name="resident_log_id", referencedColumnName="id", nullable=false)
     */
    private $residentLog;

    function getResidentLog() {
        return $this->residentLog;
    }

    function setResidentLog($residentLog) {
        $this->residentLog = $residentLog;
    }
}

ResidentLog.php

/**
 * @ORM\Entity
 * @ORM\Table(name="resident_logs")
 */
class ResidentLog
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\OneToMany(targetEntity="ResidentLogTranslation", mappedBy="residentLog", cascade={"all"}, orphanRemoval=true))
     */
    private $translations;

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

    /**
     * Add translations
     *
     * @param ResidentLogTranslation $translation
     * @return ResidentLog
     */
    public function addTranslation(ResidentLogTranslation $translation)
    {
        $translation->setResidentLog($this); // !important
        $this->translations[] = $translation;

        return $this;
    }

    /**
     * Remove translations
     *
     * @param ResidentLogTranslation $translations
     */
    public function removeTranslation(ResidentLogTranslation $translations)
    {
        $this->translations->removeElement($translations);
    }

    /**
     * Get translations
     *
     * @return \Doctrine\Common\Collections\Collection
     */
    public function getTranslations()
    {
        return $this->translations;
    }

    function setTranslations($translations) {
        $this->translations = $translations;
    }
}

ResidentLogAdmin.php

class ResidentLogAdmin extends Admin
{
    protected function configureFormFields(FormMapper $formMapper)
    {
        $formMapper
            ->add('translations', 'sonata_type_collection', array(
              'by_reference' => false // !important
            ), array(
                'edit' => 'inline',
                'inline' => 'table'
            ))
        ;
    }
}

ResidentLogTranslationAdmin.php

class ResidentLogTranslationAdmin extends Admin
{
    protected $parentAssociationMapping = 'ResidentLog';

    protected function configureFormFields(FormMapper $formMapper)
    {
        $formMapper
            ->add('language', 'sonata_type_model', array(
                'btn_add' => false
            ))
            ->add('text', 'textarea', array())
        ;
    }
}

The important part is setting by_reference to false as suggested by @webmozart here:
symfony/symfony#1540 (comment)

Probably the default value of "by_reference" had better been false (to avoid these headaches), but this would be a non-BC change now.```

Don't forget to add the `$child->setParent($this)` method on the `addChild()` method.

Related issues:
- https://github.com/sonata-project/SonataAdminBundle/issues/710
- https://github.com/sonata-project/SonataAdminBundle/issues/165