Symfony, Twig: Persistent route parameters

Question

I am making an app in Symfony3. Part of the application is sectioned by dynamic subdomains --- the subdomain is represented by a slug.

subdomains:
     host: "{slug}.{domain}"
     default:
           slug: example
     ...

When running on local example of such route would be e.g. http://a.localhost

When I create a link in Twig, either using {{ url('route') }} or {{ path('route') }}, the subdomain is always forgotten, and slug in paramenter falls to default example, always making routes http://example.localhost.

Is there a way to implicitly copy the parameters, or mark some parameters persistent, so that I do not have to make all the links include the slug like this {{ url('route', {'slug' : slug}) }}, in order to stay on the subdomain?

Thank you

Answer 1

I have created a TwigExtension for the purpose of generating links within the subdomain.

I would prefer if it were possible to make some parameters "persistent" as I mentioned in the question. Those would be implicitly carried across relative paths, but possibly nulled with explicit parameter choice. If this is not possible, I consider this better option than adding the parameter manually and best option so far.

Extension class

/**
 * ApplicationExtension constructor.
 *
 * @param Router $router
 * @param RequestStack $requestStack
 */
public function __construct(Router $router, RequestStack $requestStack)
{
    $this->router = $router;
    $this->requestStack = $requestStack;
}

public function getFunctions()
{
    return [
            new \Twig_SimpleFunction('domainPath', [
                    $this,
                    'domainPath'
            ]),
    ];
}

public function domainPath($route_name, $params = [])
{
    if (!array_key_exists('slug', $params)) {
        $params['slug'] = $this->requestStack->getCurrentRequest()->attributes->get('slug');
    }
    return $this->router->generate($route_name, $params);
}

public function getName()
{
    return 'application_extension';
}

Register service (DI and Tag)

application.twig.application_extension:
        class: ApplicationBundle\Twig\ApplicationExtension
        arguments: ["@router", "@request_stack"]
        public: false
        tags:
            - { name: twig.extension }

Use in template

{{ domainPath('route_name') }}