Symfony, How to generate Asset URL in a Twig Extension class? - symfony

Question

I have one class which extends \Twig_Extension like below :
class MYTwigExtension extends \Twig_Extension
{
protected $doctrine;
protected $router;
public function __construct(RegistryInterface $doctrine , $router)
{
$this->doctrine = $doctrine;
$this->router = $router;
}
public function auth_links($user , $request)
{
// Some other codes here ...
// HOW TO GENERATE $iconlink which is like '/path/to/an/image'
$html .= "<img src=\"$iconlink\" alt=\"\" /> ";
echo $html;
}
}
My question is How to generate Asset links in a Twig Extension ? I would like a replacement for ASSET helper in my class. Bassically I have no idea what I have to inject or use here ! Thanks in advance.
<img src="{{ asset('img/icons/modules/timesheet.png') }}" alt="" />

Answer 1

You can use the templating.helper.assets service directly.
use Symfony\Component\DependencyInjection\ContainerInterface;
public function __construct(ContainerInterface $container)
{
$this->container = $container;
}
and use it like so:
$this->container->get('templating.helper.assets')->getUrl($iconlink);
Injecting just the templating.helper.assets directly does not work in this case because the twig extension cannot be in the request scope. See the documentation here: https://symfony.com/doc/2.3/cookbook/service_container/scopes.html#using-a-service-from-a-narrower-scope

Answer 2

I didn't want to deal with the Dependency Injection Container. This is what I did:
use Twig_Environment as Environment;
class MyTwigExtension extends \Twig_Extension
{
protected $twig;
protected $assetFunction;
public function initRuntime(Environment $twig)
{
$this->twig = $twig;
}
protected function asset($asset)
{
if (empty($this->assetFunction)) {
$this->assetFunction = $this->twig->getFunction('asset')->getCallable();
}
return call_user_func($this->assetFunction, $asset);
}
I've looked at Twig_Extension class code, and found this initRuntime method there, to be overriden in our custom Extension class. It receives the Twig_Environment as an argument! This object has a getFunction method, which returns a Twig_Function instance. We only need to pass the function name (asset, in our case).
The Twig_Function object has a getCallable method, so we finally can have a callable asset function.
I've gone a bit further creating an asset method for my own extension class. Anywhere else on it, I can simply call $this->asset() and obtain the same result as {{ asset() }} in the templates.
EDIT: The getFunction call at initRuntime throws a scope exception when clearing the cache. So I moved it to the custom asset method. It works fine.

Answer 3

Here's a simple and clean way for Symfony 2.8:
services.yml:
app.twig_extension:
class: Path\To\AcmeExtension
arguments:
assets: "#templating.helper.assets"
In the TWIG extension:
use Symfony\Bundle\FrameworkBundle\Templating\Helper\AssetsHelper;
class AcmeExtension
{
protected $assets;
public function __construct(AssetsHelper $assets)
{
$this->assets = $assets;
}
}
Then you can use it in any function of the extension like this:
$this->assets->getUrl('myurl');

Answer 4

In Symfony 5.3 that worked for me:
(just do what the assets extension does and inject Packages)
use Symfony\Component\Asset\Packages;
use Twig\Extension\AbstractExtension;
use Twig\Extension\ExtensionInterface;
class AppExtension extends AbstractExtension implements ExtensionInterface
{
public function __construct(Packages $packages)
{
$this->packages = $packages;
}
// ... your other methods
private function asset($path, $packageName = null)
{
return $this->packages->getUrl($path, $packageName);
}
}

Answer 5

In Symfony 2.8 that works for me:
# services.yml
services:
app.twig_extension:
class: AppBundle\Twig\AppTwigExtension
public: false
arguments:
- #templating.helper.assets
tags:
- { name: twig.extension }
AppTwigExtension class:
namespace AppBundle\Twig;
use Symfony\Bundle\FrameworkBundle\Templating\Helper\AssetsHelper;
/**
* Class AppTwigExtension
* #package AppBundle\Twig
*/
class AppTwigExtension extends \Twig_Extension
{
const IMG_PATH = 'bundles/app/images/';
private $assetsHelper;
public function __construct(AssetsHelper $assetsHelper)
{
$this->assetsHelper = $assetsHelper;
}
public function getFilters()
{
return array(
new \Twig_SimpleFilter('img', array($this, 'imagePathFilter'))
);
}
/**
* Get image path relatively to host
* Usage in Twig template: {{ 'my_image.png'|img }} - equal to
* {{ asset('bundles/app/images/my_image.png') }} in Twig template:
*
* #param string $imageName (e.g. my_image.png)
* #return string
*/
public function imagePathFilter($imageName)
{
return $this->assetsHelper->getUrl(self::IMG_PATH . $imageName);
}
public function getName()
{
return 'app_twig_extension';
}
}