How can I make route parameters optional in a routing callback?

Question

I needed to create a route in which the path of the route would be completely dynamic and so I created a routing callback.

<?php

namespace Drupal\uber_affiliate\Routing;

use Symfony\Component\Routing\Route;
use Symfony\Component\Routing\RouteCollection;

/**
 * Class EntityOverview
 *
 * @package Drupal\uber_affiliate\Routing
 */
class AffiliateRoute {

  /**
   * Dynamically generate the routes for the entity details.
   *
   * @return \Symfony\Component\Routing\RouteCollection
   * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
   */
  public function routes() {

    $affiliate_menu_path = \Drupal::state()->get('affiliate_module_affiliate_menu_path', 'affiliate');
    $routes = [];
    $routes['affiliate'] = new Route(
      $affiliate_menu_path . '/' .   '{aff_id}' . '/' . '{dest_path}' . '/' . '{tracker_id}',
      [
        '_controller' => 'Drupal\uber_affiliate\Controller\UberAffiliate::affiliate_page',
      ],
      [
        '_permission'  => 'track affiliate clicks for this role',
      ],
      );


    return $routes;
  }
}

I need {dest_path} and {tracker_id} to be optional. How do I make them optional?

Answer 1

You can do so by providing a default value for those parameters.

path: '/foo/bar/{baz}'
defaults:
  ...
  baz: 'fallback-value'

With your example, it should be something like:

$routes['affiliate'] = new Route(
  "{$affiliate_menu_path}/{aff_id}/{dest_path}/{tracker_id}",
  [
    '_controller' => 'Drupal\uber_affiliate\Controller\UberAffiliate::affiliate_page',
    'dest_path' => 'fallback',
    'tracker_id' => 'fallback',
  ],
  [
    '_permission'  => 'track affiliate clicks for this role',
  ]
);

I assume there is a reason why you want them as route parameters and not as query string parameters (i.e. ?destination=foo&tracker-id=bar).

See Optional parameters for more info.