ManyToOne in a twig template

I have the following tables (and entities in symfony2 / doctrine2):

+------------------+                  +--------------------+
|  forum_sections  |                  |  forum_categories  |
+------------------+                  +--------------------+
| id               ├--------|         | id                 |
| title            |        |---------| section            |
| position         |                  | position           |
| created_at       |                  | title              |
+------------------+                  | description        |
                                      +--------------------+

I want to archive the following html page (without the bullets ofcource):

this is a title (from forum_sections->title)
- forum 1 (from forum_categories->title)
- forum 2 (from forum_categories->title)
this is another title (from forum_sections->title)
- forum 3 (from forum_categories->title)

I did some research on how to do this. So far I tried the following in my twig layout:

{% for section in sections %}
    <h1>title</h1>

    {% for category in categories %}
        bla bla
    {% endfor %}
{% endfor %}

Is this even possible with a 'findAll' query in Doctrine2? I tried some combinations, but they seem to get all the boards ignoring the sections.

Solution

I think the problem is in your entities, the way you define the relationship between entitites. You need to use bidirectional mapping http://doctrine-orm.readthedocs.org/en/latest/reference/association-mapping.html#one-to-many-bidirectional

I updated your entities to fit your needs.

Added categories to ForumSection entity
Added addCategory(), removeCategory(), getCategories() methods to ForumSection entity
Added inversedBy annotation to ForumCategory entity to complete te relationship
I used getCategories() method to get all the categories for the section in twig.

The entities;

ForumSection.php

namespace AppBundle\Entity;

/**
 *  @version    0.0.1
 *  @copyright  (c) 2015 Ricardo Jacobs. All rights reserved.
 *  @license    Proprietary and confidential source code.
 */

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

/**
 * @ORM\Entity(repositoryClass="AppBundle\Entity\Repositories\Forum")
 * @ORM\HasLifecycleCallbacks
 * @ORM\Table(name="forum_sections")
 */
class ForumSection
{
    /**
     * @ORM\Column(type="integer", name="id")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255, name="title")
     */
    private $title;

    /**
     * @ORM\Column(type="integer", name="position")
     */
    private $position;

    /**
     * @ORM\Column(type="datetime")
     */
    private $created_at;

    /**
     * @ORM\OneToMany(targetEntity="AppBundle\Entity\ForumCategory", mappedBy="section")
     */
    private $categories;


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

    public function getCategories() {
       return $this->categories;
    }

    /**
     * Add category
     *
     * @param AppBundle\Entity\ForumCategory
     * @return ForumSection
     */
    public function addCategory(\AppBundle\Entity\ForumCategory $category)
    {
        $this->categories[] = $category;

        return $this;
    }

    /**
     * Remove category
     *
     * @param AppBundle\Entity\ForumCategory $category
     */
    public function removeCategory(\AppBundle\Entity\ForumCategory $category)
    {
        $this->categories->removeElement($category);
    }



    /**
     * @ORM\PrePersist
     * @ORM\PreUpdate
     */
    public function updatedTimestamps() {
        if ($this->getCreatedAt() == null) {
            $this->setCreatedAt(new \DateTime('NOW'));
        }
    }

    /**
     * @return mixed
     */
    public function getId() {
        return $this->id;
    }

    /**
     * @return mixed
     */
    public function getTitle() {
        return $this->title;
    }

    /**
     * @param $title
     * @return $this
     */
    public function setTitle($title) {
        $this->title = $title;

        return $this;
    }

    /**
     * @return mixed
     */
    public function getPosition() {
        return $this->position;
    }

    /**
     * @param $position
     * @return $this
     */
    public function setPosition($position) {
        $this->position = $position;

        return $this;
    }

    /**
     * @return Date
     */
    public function getCreatedAt() {
        return $this->created_at;
    }

    /**
     * @param $date
     */
    public function setCreatedAt($date) {
        $this->created_at = $date;

        return $this;
    }
}

ForumCategory.php

<?php

namespace AppBundle\Entity;

/**
 *  @version    0.0.1
 *  @copyright  (c) 2015 Ricardo Jacobs. All rights reserved.
 *  @license    Proprietary and confidential source code.
 */

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity(repositoryClass="AppBundle\Entity\Repositories\Forum")
 * @ORM\Table(name="forum_categories")
 */
class ForumCategory
{
    /**
     * @ORM\Column(type="integer", name="id")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\ManyToOne(targetEntity="AppBundle\Entity\ForumSection", inversedBy="categories")
     * @ORM\JoinColumn(name="section", referencedColumnName="id")
     */
    private $section;

    /**
     * @ORM\Column(type="integer", name="position")
     */
    private $position;

    /**
     * @ORM\Column(type="string", length=255, name="title")
     */
    private $title;

    /**
     * @ORM\Column(type="string", length=255, nullable=true, name="description")
     */
    private $description;

    /**
     * @return mixed
     */
    public function getId() {
        return $this->id;
    }

    /**
     * @return mixed
     */
    public function getSection() {
        return $this->section;
    }

    /**
     * @param $section
     * @return $this
     */
    public function setSection($section) {
        $this->section = $section;

        return $this;
    }

    /**
     * @return mixed
     */
    public function getPosition() {
        return $this->position;
    }

    /**
     * @param $position
     * @return $this
     */
    public function setPosition($position) {
        $this->position = $position;

        return $this;
    }

    /**
     * @return mixed
     */
    public function getTitle() {
        return $this->title;
    }

    /**
     * @param $title
     * @return $this
     */
    public function setTitle($title) {
        $this->title = $title;

        return $this;
    }

    /**
     * @return mixed
     */
    public function getDescription() {
        return $this->description;
    }

    /**
     * @param $description
     * @return $this
     */
    public function setDescription($description) {
        $this->description = $description;

        return $this;
    }
}

The controller;

public function indexAction()
{
    $em = $this->get('doctrine')->getManager();
    $sections = $sections = $this->getDoctrine() ->getRepository('AppBundle:ForumSection') ->findAll();

    return $this->render('AppBundle:Default:index.html.twig', array('sections'=>$sections));
 }

The template;

<ol>
    {% for forum in sections %}
        <li>
            <h2>{{forum.title}} </h2>
            <ul>
                {% for category in forum.getCategories() %}
                    <li>{{category.title}}</li>
                {% endfor %}
            </ul>
        </li>   
    {% endfor %}
</ol>

Now you have access to categories related to each forum_section row in your database.

And this is the output after I run the code

hello
- hello section 1
- hello section 2

world
- world section 1
- world section 2

I have to mention that Doctrine uses lazy loading by default.Doctrine will perform extra queries to find categories related to forums. If you have n forums you will have n + 1 queries. In my case I used 2 forum sections and here are the queries.

This one finds all the forum_sections;

SELECT t0.id AS id1, t0.title AS title2, t0.position AS position3, t0.created_at AS created_at4 FROM forum_sections t0

Then for each forum, doctrine executes another query to find categories with different parameters. This queries don't get executed untill you call 'forum.getCategories()` method.

SELECT t0.id AS id1, t0.position AS position2, t0.title AS title3, t0.description AS description4, t0.section AS section5 FROM forum_categories t0 WHERE t0.section = ? [Parameters: 1,2] Check out fetch-join concept to learn more about lazy loading and alternatives. http://blog.bemycto.com/good-practices/2015-05-31/understanding-doctrine-orm-lazy-load-fetch-join/

ManyToOne in a twig template

hello

world