ZF2 navigation auto-inject to viewmodel

Module.php

<?php

namespace Application;

use Zend\EventManager\EventInterface;
use Zend\ModuleManager\Feature\BootstrapListenerInterface;

class Module implements BootstrapListenerInterface,
{
    /**
     * {@inheritDoc}
     */
  public function onBootstrap(EventInterface $event)
	{
        $application    = $event->getParam('application');
        $serviceManager = $application->getServiceManager();
        $eventManager   = $application->getEventManager();

        $eventManager->attach('render', array($this, 'injectNavigationIntoViewModel'));
	}
  
  public function injectNavigationIntoViewModel($event)
    {
        $model = $event->getViewModel();
        
        if (get_class($model) != 'Zend\View\Model\ViewModel') {
            // We compare class instead of instance since some models might extend viewmodel.
            return;
        }
        
        $app = $event->getApplication();
        $sm  = $app->getServiceManager();
        $model->setVariable('navigation', $sm->get('Navigation'));
    }
}