通过Symfony的BundleExtention类设置参数，而不是使用twig global

So I am trying to wrap my head around how to set parameters via the BundleNameExtention class that resides inside the DependencyInjection folder of a bundle rather than defining them directly in config.yml

I am using a default AppBundle that came with symfony install.

It seems pretty straight forward reading the documentation online that inside the load method I should be able to set the parameters I want so this is what I did

namespace AppBundle\DependencyInjection;

use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\Config\FileLocator;
use Symfony\Component\HttpKernel\DependencyInjection\Extension;
use Symfony\Component\DependencyInjection\Loader;

class AppExtension extends Extension
{
    public function load(array $configs, ContainerBuilder $container)
    {


        $loader = new Loader\xmlFileLoader($container, new FileLocator(__DIR__.'/../Resources/config'));
        $loader->load('services.xml');

        $configuration = new Configuration();
        $config = $this->processConfiguration($configuration, $configs);
        $config['comments'] = "some value";
        $container->setParameter('app.comments', $config['comments']);


    }

    public function getAlias(){
        return 'app';

    }
}

How can I access this parameter in my twig template?

Okay so this is what I ended up doing to achieve it.

Inside the DependencyInjection folder of a bundle along with AppExtension class I had to use Configuration class as well which implements ConfigurationInterface Docs

My AppExtension class

namespace AppBundle\DependencyInjection;

use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\Config\FileLocator;
use Symfony\Component\HttpKernel\DependencyInjection\Extension;
use Symfony\Component\DependencyInjection\Loader;

class AppExtension extends Extension
{

    public function load(array $configs, ContainerBuilder $container)
    {    

        $loader = new Loader\xmlFileLoader($container, new FileLocator(__DIR__ . '/../Resources/config'));
        $loader->load('services.xml');

        $configuration = new Configuration();
        $config = $this->processConfiguration($configuration, $configs);

        $container->setParameter('app.comments', $config['comments']);

    }

    public function getAlias()
    {
        return 'app';

    }

}

This is my Configuration class

namespace AppBundle\DependencyInjection;

use Symfony\Component\Config\Definition\Builder\TreeBuilder;
use Symfony\Component\Config\Definition\ConfigurationInterface;

class Configuration implements ConfigurationInterface
{
    public function getConfigTreeBuilder()
    {
        $treeBuilder = new TreeBuilder();
        $rootNode = $treeBuilder->root('app');
        $rootNode->children()->scalarNode('comments')->end();
        return $treeBuilder;
    }
}

And finally inside my app/config/config.yml

app:
    comments: 'some value'

Now to access this simply fetch it via controller and pass it to the twig template.

$comments = $this->container->getParameter( 'app.comments' );
return $this->render('default/index.html.twig', array('comments' => $comments));

This works for me, hopefully it will help someone else too

You can actually, you'll have to implement the use Symfony\Component\DependencyInjection\Extension\PrependExtensionInterface; interface in your extension class, and add the following prepend function:

class AppExtension extends Extension implements PrependExtensionInterface{

    // ... your other code 

    public function prepend(ContainerBuilder $container){
        $configs = $container->getExtensionConfig($this->getAlias());
        $config = $this->processConfiguration(new Configuration(), $configs);
        $container->prependExtensionConfig('twig', array(
            'globals' => array('app_comments', $config['comments'])));
    }

}

Now you will have access to app_comments in all your templates.