How to Work with Doctrine Associations / Relations dosen't work - symfony

Question

I trying make relation in symphony through this http://symfony.com/doc/current/doctrine/associations.html
problemm is that when i get post and wont get related entitie (rss) i get null
<?php
namespace AppBundle\Entity;
use Doctrine\ORM\Mapping as ORM;
/**
* Post
* #ORM\Entity
* #ORM\Table(name="post")
*/
class Post
{
/**
* #var int
*/
private $id;
/**
* #var string
*/
private $title;
/**
* #var string
*/
private $text;
/**
* #ORM\ManyToOne(targetEntity="Rss", inversedBy="posts")
* #ORM\JoinColumn(name="link", referencedColumnName="id")
*/
private $rss;
/**
* #var \DateTime
*/
private $createdAt;
/**
* Get id
*
* #return int
*/
public function getId()
{
return $this->id;
}
/**
* Set title
*
* #param string $title
*
* #return Post
*/
public function setTitle($title)
{
$this->title = $title;
return $this;
}
/**
* Get title
*
* #return string
*/
public function getTitle()
{
return $this->title;
}
/**
* Set text
*
* #param string $text
*
* #return Post
*/
public function setText($text)
{
$this->text = $text;
return $this;
}
/**
* Get text
*
* #return string
*/
public function getText()
{
return $this->text;
}
/**
* Set link
*
* #param string $link
*
* #return Post
*/
public function setLink($link)
{
$this->link = $link;
return $this;
}
/**
* Get link
*
* #return string
*/
public function getLink()
{
return $this->link;
}
/**
* Set createdAt
*
* #param \DateTime $createdAt
*
* #return Post
*/
public function setCreatedAt($createdAt)
{
$this->createdAt = $createdAt;
return $this;
}
/**
* Get createdAt
*
* #return \DateTime
*/
public function getCreatedAt()
{
return $this->createdAt;
}
/**
* #var integer
*/
private $user_id;
/**
* Set userId
*
* #param integer $userId
*
* #return Post
*/
public function setUserId($userId)
{
$this->user_id = $userId;
return $this;
}
/**
* Get userId
*
* #return integer
*/
public function getUserId()
{
return $this->user_id;
}
/**
* #var integer
*/
private $link;
public function setRss($rss){
$this->rss = $rss;
}
public function getRss(){
return $this->rss;
}
}
<?php
namespace AppBundle\Entity;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\ORM\Mapping as ORM;
/**
* rss
*
* #ORM\Entity
* #ORM\Table(name="rss")
*/
class Rss
{
/**
* #var int
*/
private $id;
/**
* #var string
*/
private $name;
/**
* #var string
*/
private $address;
/**
* Get id
*
* #return int
*/
public function getId()
{
return $this->id;
}
/**
* Set name
*
* #param string $name
*
* #return rss
*/
public function setName($name)
{
$this->name = $name;
return $this;
}
/**
* Get name
*
* #return string
*/
public function getName()
{
return $this->name;
}
/**
* Set address
*
* #param string $address
*
* #return rss
*/
public function setAddress($address)
{
$this->address = $address;
return $this;
}
/**
* Get address
*
* #return string
*/
public function getAddress()
{
return $this->address;
}
/**
* #var \DateTime
*/
private $lastUpdate;
/**
* #ORM\OneToMany(targetEntity="Post", mappedBy="Rss")
*/
private $posts;
public function __construct()
{
$this->posts = new ArrayCollection();
}
public function getPosts(){
return $this->posts;
}
public function setPosts($posts){
$this->posts[] = $posts;
}
/**
* Set lastUpdate
*
* #param \DateTime $lastUpdate
*
* #return rss
*/
public function setLastUpdate($lastUpdate)
{
$this->lastUpdate = $lastUpdate;
return $this;
}
/**
* Get lastUpdate
*
* #return \DateTime
*/
public function getLastUpdate()
{
return $this->lastUpdate;
}
/**
* #var string
*/
private $pageaddress;
/**
* Set pageaddress
*
* #param string $pageaddress
*
* #return rss
*/
public function setPageaddress($pageaddress)
{
$this->pageaddress = $pageaddress;
return $this;
}
/**
* Get pageaddress
*
* #return string
*/
public function getPageaddress()
{
return $this->pageaddress;
}
}
public function indexAction()
{
$em = $this->getDoctrine()->getManager();
$posts = $em->getRepository('AppBundle:Post')->findAll();
$post = $this->getDoctrine()
->getRepository('AppBundle:Post')
->find(1);
$post->getRss();

Answer 1

This can help you:
https://knpuniversity.com/screencast/doctrine-relations/many-to-one-relation
also you can try modifying the variable $id
private $id
for
/**
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
* #ORM\Column(type="integer")
*/
private $id;
To create a primary key.
Entity
class Post
/**
* #ORM\ManyToOne(targetEntity="Rss", inversedBy="post")
* #ORM\JoinColumn(nullable=false)
*/
private $rss;
class Rss
/**
* #ORM\OneToMany(targetEntity="Post", mappedBy="rss")
* #ORM\OrderBy({"createdAt"="DESC"})
*/
private $post;
and the class Post you will need to create a constructor like this
public function __construct()
{
$this->posts = new ArrayCollection();
}
/**
* #return ArrayCollection|GenusNote[]
*/
public function getPosts()
{
return $this->notes;
}
I hope it can help you