add Twig Extension.md

My Guru helped me to add a service for my module made with modulestudio for zikula. This example is for https://github.com/rallek/showroom

The Twig Extension should me help to find out the name of the first level (showRoomItem) of its stories and substories. Stories do have a self relation and can have endless levels.

declaration of the service

you do need a yml file to create the service. I got this code:

services:
    rk_showroom_module.custom_twig_extension:
        class: RK\ShowRoomModule\Twig\CustomTwigExtension
        public: true
        tags:
            - { name: twig.extension }

Be shure not to use tab. In yml files we have to use spaces. This code should be placed inside Resources/config/customServices.yml

adding the service

to make this service known for the module you have to add this inside the file Resources/config/services.yml. at the edn you have to add

  - { resource: 'customServices.yml' }

To avoid overwriting by a new generated version of the module you should add this file to the markFiles inside the setting container of modulestudio.

creating the extension

Now we do need the extension itself. For this we add a file Twig\CustomTwigExtension.php (see the class: in our service declaration)

This file do get the following code:

<?php
namespace RK\ShowRoomModule\Twig;

use Twig_Extension;
use RK\ShowRoomModule\Entity\ShowRoomItemEntity;
use RK\ShowRoomModule\Entity\StoryEntity;

/**
 * Custom Twig extension implementation class.
 */
class CustomTwigExtension extends Twig_Extension
{
    /**
     * Returns a list of custom Twig functions.
     *
     * @return array
     */
    public function getFunctions()
    {
        return [
            new \Twig_SimpleFunction('rkshowroommodule_getShowRoomItemForStory', [$this, 'getShowRoomItemForStory'])
        ];
    }

    /**
     * Returns the show room item for a given story.
     *
     * @param StoryEntity $story Story entity
     *
     * @return ShowRoomItemEntity|null
     */
    public function getShowRoomItemForStory(StoryEntity $story)
    {
        $showRoomItem = null;
        $parentStory = $story;
        while (null === $showRoomItem && null !== $parentStory) {
            $showRoomItem = $parentStory->getShowRoomItem();
            $parentStory = $parentStory->getStory();
        }

        return $showRoomItem;
    }
}

Using in a template

To print the title of the root element you have to run this code:

{% set storyShowRoomItem = rkshowroommodule_getShowRoomItemForStory(story) %}
{% if storyShowRoomItem is not empty %}
    <p>{{ storyShowRoomItem.title }}</p>
{% endif %}

more Twig Extensions?

you can add more Twig Extensions into CustomTwigExtension.php. This way to implement avoids to touch generated code.