Get field from related model in Volt

Hei,

I try to understand related models, so I created a small setup for a gallery. Now I want to get an ID from a related model. But I do not know how to use it in volt.

So I would like to create a menu with links to the categories. Working. And I want to display the pictures; also working. But now I want to display the corresponding category-ID to each picture. How can I get the ID within the loop for the pictures?

This is my database setup:

CREATE TABLE IF NOT EXISTS `gallery_categories` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `icon` varchar(64) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=3 ;

INSERT INTO `gallery_categories` (`id`, `name`, `icon`) VALUES
(1, 'Default', 'fa-bars'),
(2, 'Testcat', 'fa-angle-down');

-- --------------------------------------------------------

CREATE TABLE IF NOT EXISTS `gallery_items` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `path` varchar(128) NOT NULL,
  `title` varchar(32) NOT NULL,
  `subtitle` varchar(64) NOT NULL,
  `description` varchar(512) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=6 ;

INSERT INTO `gallery_items` (`id`, `path`, `title`, `subtitle`, `description`) VALUES
(1, 'https://lorempixel.com/262/262/technics/', 'Title #1', 'This is a small placeholder', 'This placeholder is holding place. A place that could be filled with some thing else.'),
(2, 'https://lorempixel.com/262/262/technics/', 'Title #1', 'This is a small placeholder', 'This placeholder is holding place. A place that could be filled with some thing else.'),
(3, 'https://lorempixel.com/262/262/technics/', 'Title #1', 'This is a small placeholder', 'This placeholder is holding place. A place that could be filled with some thing else.');

-- --------------------------------------------------------

CREATE TABLE IF NOT EXISTS `gallery_memberships` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `gallery_item_id` int(10) NOT NULL,
  `gallery_category_id` int(10) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `robots_id` (`gallery_item_id`),
  KEY `parts_id` (`gallery_category_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=6 ;

INSERT INTO `gallery_memberships` (`id`, `gallery_item_id`, `gallery_category_id`) VALUES
(1, 1, 1),
(2, 1, 2),
(4, 2, 1),
(5, 3, 1);

So here we go with the models:

// GalleryCategories.php
<?php
namespace Vokuro\Models;
use Phalcon\Mvc\Model;

class GalleryCategories extends Model
{
    public $id;

    public $name;

    public $icon;

    public function initialize()
    {
        $this->hasMany("id", "Vokuro\Models\GalleryMemberships", "gallery_category_id", array( "alias" => "GalleryMemberships"));
    }

}

// GalleryItems.php
<?php
namespace Vokuro\Models;
use Phalcon\Mvc\Model;

class GalleryItems extends Model
{
    public $id;

    public $path;

    public $title;

    public $subtitle;

    public $description;

    public function initialize()
    {
        $this->hasMany("id", "Vokuro\Models\GalleryMemberships", "gallery_item_id", array( "alias" => "GalleryMemberships"));
    }

}

// GalleryMemberships.php
<?php
namespace Vokuro\Models;
use Phalcon\Mvc\Model;

class GalleryMemberships extends Model
{
    public $id;

    public $gallery_item_id;

    public $gallery_category_id;

    public function initialize()
    {
        $this->belongsTo("gallery_item_id", "Vokuro\Models\GalleryItems", "id", array( "alias" => "GalleryItems"));
        $this->belongsTo("gallery_category_id", "Vokuro\Models\GalleryCategories", "id", array( "alias" => "GalleryCategories"));
    }

}

And the controller:

<?php
namespace Vokuro\Controllers;
use Vokuro\Models\GalleryItems;
use Vokuro\Models\GalleryCategories;
/**
 * Display the default index page.
 */
class GalleryController extends ControllerBase
{
    public function initialize()
    {
        $this->view->setTemplateBefore('public');
    }

    /**
     * Default action. Set the public layout (layouts/public.volt)
     */
    public function indexAction()
    {
        // Get all categories
        $this->view->setVar("gallery_categories", GalleryCategories::find());
        $this->view->setVar("gallery_items", Galleryitems::find());
    }
}

And here comes the template index.volt

    /////////////////////////////////////////////////////
    {{ codeblock to display a menu based on categories }}
    /////////////////////////////////////////////////////

    {% for gallery_category in gallery_categories %}
    <li>
        <a class="" href="#filter" data-option-value=".category-{{ gallery_category.id }}">
            <i class="fa {{ gallery_category.icon }}"></i>
            <span class="title">{{ gallery_category.name }}</span>
        </a>
    </li> 
    {% endfor  %}

    /////////////////////////////////////////////////////
    {{ codeblock to display pictures }}
    /////////////////////////////////////////////////////

    {% for gallery_item in gallery_items %}

    <div class="col-md-3 col-xs-12 col-sm-6 bottom-30 element category-{{ HERE I NEED THE CATEGORY ID }}" data-my-order="1">
        <div class="portfolio-item white">
            <div class="portfolio-info">
                <h4><a href="#">{{ gallery_item.title }}</a></h4>
                <a href="#">{{ gallery_item.subtitle }}</a>
            </div>
            <div class="portfolio-image">
                <a href="#"><img src="{{ gallery_item.path }}" alt=""></a>
            </div>
            <div class="portfolio-link">
                <a href="#"><i class="fa fa-eye"></i>View Detail</a>
                <a title="{{ gallery_item.description }}" class="image-popup" href="https://placehold.it/800x800"><i class="fa fa-search-plus"></i>Quick View</a>
            </div> 
        </div> 
    </div> 

    {% endfor %}

Hope you get my idea. :)