Using Twig in a custom Twig Extension

Question

In a Symfony2 project, I have created a service that implements Twig_ExtensionInterface so I can use it as a Twig filter, like {{ stuff|my_filter }}

In this service, I need to use the twig environnement so I could use twig templates for instance, so I injected it as one can do in a service :

in services.yml :

services:
    meta.twig.my_extension:
        class: Acme\GeneralBundle\Twig\MyExtension
        tags:
            - { name: twig.extension }
        arguments:
            twig: "@twig"

And so the service in itself looks like :

<?php

namespace Acme\GeneralBundle\Twig;

class MyExtension extends \Twig_Extension
{

    public function __construct($twig)
    {
        $this->twig = $twig;
    }

    public function getFilters()
    {
        return array(
            'my_filter' => new \Twig_Filter_Method($this, 'myFunction'),
        );
    }

    public function myFunction($text)
    {
       return $this->twig->render($someTemplate,$someArguments);
    }
}

And I can use it in a controller like that :

$myService = $this->container->get('Acme.twig.my_extension');
$text = $myService->myFunction($someValue);

But, of course, I get a CircularReference Error when doing so:

Circular reference detected for service "Acme.twig.my_extension", 
path: "Acme.twig.my_extension -> twig".

So, what is the best way to use twig->render() function inside a custom Twig Filter ?

Thanks a lot !

What version of symfony do you use? At 2.1 I do not see issue and such example as yours work without problems. You can try inject container instead of twig_env and lazy load twig. — l3l0
– l3l0, Commented Feb 1, 2013 at 22:19
I'm using version 2.1.8-DEV but this very example does not work. I understand that injecting the whole container is bad practice that's why I went this route... to no avail since effectively the twig environment seems to be "recursively injected" somehow. I could not find any literature on the web for a good solution though — tchap
– tchap, Commented Feb 1, 2013 at 23:06
Have you tried removing both the constructor of your extension and the arguments part on the services file? DIC should take care of that for you. — Diego Agulló
– Diego Agulló, Commented Feb 2, 2013 at 2:22
But then @DiegoAgulló how do I call the render() function of the Twig_Environment ? $this does not have such a method ... — tchap
– tchap, Commented Feb 2, 2013 at 13:18
I think you shouldn't need to do that in the first place. When defining a filter your method receives some parameters and returns a transformed string/int/whatever. — Diego Agulló
– Diego Agulló, Commented Feb 2, 2013 at 13:38

Jakub Zalas · Accepted Answer · 2013-02-02 19:57:23Z

3

Twig_ExtensionInterface defines the initRuntime() method which accepts the twig environment as an argument. This method is called by twig while initialising the extension.

You've extended the Twig_Extension class, which already provides an empty implementation of this method. All you have to do is overwrite it and store a reference to the twig environment for future use.

<?php

namespace Acme\GeneralBundle\Twig;

class MyExtension extends \Twig_Extension
{
    private $environment = null;

    public function initRuntime(\Twig_Environment $environment)
    {
        $this->environment = $environment;
    }

    public function getFilters()
    {
        return array(
            'my_filter' => new \Twig_Filter_Method($this, 'myFunction'),
        );
    }

    public function myFunction($text)
    {
       return $this->environment->render($someTemplate,$someArguments);
    }
}

Documentation: Creating an extension.

answered Feb 2, 2013 at 19:57

Jakub Zalas

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2 Comments

tchap Over a year ago

Yes, this works when I'm using the service in a twig template for sure. But then how do I call it as a service as per : $myService = $this->container->get('Acme.twig.my_extension'); $text = $myService->myFunction($someValue); ... I need to pass the twig environment somehow

Jakub Zalas Over a year ago

Twig environment calls the method automatically in loadTemplate(). I guess you could force it by calling $twig->initRuntime() which will initialise all the extensions.

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