Twig extension issues

Question

I'm trying to write a simple twig extension to render a menu inside twig template files.

I created a custom module for this purpose. It's folder structure looks like this:

-modules
--MenuRender
---src
----MenuRenderExtension.php
--menurender.info.yml
--menurender.services.yml

The *.info file is a standard file, the *.services files looks like this:

services:
  menurender.twig_extension:
    class: Drupal\MenuRender\MenuRenderExtension
    tags:
      - { name: twig.extension }

And the MenuRenderExtension class is as follows:

namespace Drupal\MenuRender;

class MenuRenderExtension extends \Twig_Extension {

  public function getName() {
    return 'MODULE.twig_extension';
  }

  /**
   * @return array
   */
  public function getFunctions() {
    return [
      new \Twig_SimpleFunction('renderMenu', [$this, 'renderMenu'])
    ];
  }

  /**
   * Provides function to programmatically rendering a menu
   *
   * @param String $menu_name
   *   The machine configuration id of the menu to render
   */
  public function renderMenu($menu_name) {
    // 50+ lines so i cut this part as it's mostly clean PHP
  }

}

I am constantly getting this error msg in apache's error log

Service 'menurender.twig_extension' for consumer 'twig' does not implement Twig_ExtensionInterface

Any one have a clue ? p.s. new to drupal8

Answer 1

Your module name should not be camel case, but should instead be mymodule (not MenuRender). Your namespace needs to reflect that, too. It should likely live under a folder in src called TwigExtension, and your module name in the namespace should match the directory (i.e. Drupal\mymodule, not Drupal\MyModule).

Here is a module that uses TwigExtension for comparison.

What's likely happening is the application is unable to locate certain things due to the file naming and namespacing.