Learn it the soft way: OneToMany relationship in Doctrine2 and Symfony2 for dummies

It may seem obvious to a lot, but ...

THE CLASSES

In a forum, there are Authors. These authors can post messages. Every Message has one and only one Author, and an Author can write many Messages : this is typically a OneToMany relationship.
Here are the equivalent classes :

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/**  * @ORM\Entity  * @ORM\Table(name="Author")  * @ORM\Entity(repositoryClass="Acme\DemoBundle\AuthorRepository")  */ class Author {        /**      * @ORM\Id      * @ORM\Column(type="integer")      * @ORM\GeneratedValue(strategy="AUTO")      * @var int      */     protected $id;        /**      * @ORM\OneToMany(targetEntity="Message", mappedBy="author", cascade={"persist", "remove"})      */     protected $messages;           /**      * Add message      *      * @param Acme\DemoBundle\Entity\Message $message      */     public function addMessage(Acme\DemoBundle\Entity\Message $message)     {         $this->mesages[] = $message;         $message->setAuthor($this);         return $this;     }           /**      * Get messages      *      * @return Doctrine\Common\Collections\Collection      */     public function getMessages()     {         return $this->messages;     }             public function __construct()     {         $this->messages = new \Doctrine\Common\Collections\ArrayCollection();     } }     /**  * @ORM\Entity  * @ORM\Table(name="Message")  * @ORM\Entity(repositoryClass="Acme\DemoBundle\Repository\MessageRepository")  */ class Message {     /**      * @ORM\Id      * @ORM\Column(type="integer")      * @ORM\GeneratedValue(strategy="AUTO")      * @var int      */     protected $id;           /**      * @ORM\ManyToOne(targetEntity="Author", inversedBy="messages", cascade={"persist", "update"})      * @ORM\JoinColumn(name="author_id", referencedColumnName="id", onDelete="cascade", onUpdate="cascade")      * @var Acme\DemoBundle\Entity\Author      */     protected $author;       }

THE ISSUE

Now, let's say you want to transfer messages from author 2 to author 1 for some reason. Here is how to do it step by step :

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// Get the entities $Author1 = $authorRepository->find($idAuthor1); $Author2 = $authorRepository->find($idAuthor2);   // Retrieve messages $messagesOfAuthor2 = $Author2->getMessages();

Here is a visual description of what has happened :

State 0 :

We transfer each of the messages :

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// Move message foreach($messagesOfAuthor2 as $message) {     $Author1->addMessage($message);     // Leads to state 1     $Author2->getMessages()->removeElement($message);     // Leads to state 2 }

State 1 :

State 2 :

Note the deletion of 1 link in the removeElement function, and the addition of 2 links in the addMessage function.
We can now remove the Author 2 and flush the EntityManager :

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$entityManager->remove($Author2);   $entityManager->flush();

Learn it the soft way: OneToMany relationship in Doctrine2 and Symfony2 for dummies

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