Symfony2 Extend Twig Block in Event Listener

Question

I'm trying to find a way to extend a known twig block in an event listener/subscriber.

The code is very basic.

Main twig:

<!doctype html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>Hello World</title>
</head>
<body>

{% block body %}{% endblock %}

{% block javascripts %}{% endblock %}

</body>
</html>

As you can see it's just a plain html with 2 blocks: body and javascripts.

Now for example I've a event listener onKernelResponse. What I want here is to be able to add new javascript to the "javascripts" block with twig's "extends".

The code could be something like:

public function onKernelResponse(FilterResponseEvent $event)
{
    if (HttpKernelInterface::MASTER_REQUEST !== $event->getRequestType()) {
        return;
    }

    $response = $event->getResponse();

    //complete guesswork code to illustrate what I'm trying to achieve

    $content =  $this->twig->extend( //extend() function is imaginary
        $response, //pass in current response
        'AcmeBundle:Javascript:index.html.twig',
    );
    $response->setContent($content);
}

The $this->twig->extend should work like $this->twig->render, but instead of render something new, extend() should take the $response and extend it with the 'AcmeBundle:Javascript:index.html.twig' where I can add more content to the "javascripts" block.

Here is the example of the "AcmeBundle:Javascript:index.html.twig":

{% block javascripts %}
    {{ parent() }}

    <script>
        var something = "new";
    </script>
{% endblock %}

Basically I'm looking for a way to programatically extend twig block in event listeners.

Thanks for the help in advance.

Nicolai Fröhlich Nicolai Fröhlich · Accepted Answer · 2013-08-06T02:33:55

You can register a twig global variable in the event listener to indicate wether to extend the block.

... or you can include the global variable registered in your event listener as template code somewhat similar to eval using twig's template_from_string() function.

{% block javascripts %}
    {{ parent() }} 
    {{ include(template_from_string(global_variable_name|default(''))) }}
{% endblock %}

Symfony2 Extend Twig Block in Event Listener

1 Answers