How to create a dynamic routes in Drupal 8

To generate a dynamic routes, we start off with the route_callbacks method.

To begin, you just add the method in your routing.yml with the callback to your class and method:

route_callbacks:
  - '\Drupal\mymodule\Routing\MyModuleRoutes::routes'

Then you just need to make a Routing class and slap in your logic. Basically you are creating the YAML version of the typical route in PHP in the routes method.

in this class also I Inject config.factory service to get dynamic params from config form.

<?php

namespace Drupal\mymodule\Routing;

use Drupal\Core\Config\ConfigFactoryInterface;
use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\Routing\Route;

/**
 * Class MyModuleRoutes
 * @package Drupal\mymodule\Routing
 */
class MyModuleRoutes implements ContainerInjectionInterface {

  /**
   * @var \Drupal\Core\Config\ImmutableConfig
   */
  protected $config;

  /**
   * MyModuleRoutes constructor.
   * @param ConfigFactoryInterface $config_factory
   */
  public function __construct(ConfigFactoryInterface $config_factory) {
    $this->config = $config_factory->get('mymodule.settings');
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static(
      $container->get('config.factory')
    );
  }


  /**
   * {@inheritdoc}
   */
  public function routes()
  {
    $routes = [];
    $pid = 1;
//    $path = '/example';
    $path = $this->config->get('path_page');

    $routes['mymodule.page_' . $pid] = new Route(
      $path,
      [
        '_controller' => '\Drupal\mymodule\Controller\MyModuleController::index',
        '_title' => 'Hello'
      ],
      [
        '_permission' => 'access content',
      ]
    );

    return $routes;
  }


}

As you can see this is basically adding another layer between the routing.yml and the Controller. Here is what our Controller looks like this:

<?php
namespace Drupal\mymodule\Controller;

use Drupal\Core\Controller\ControllerBase;


class MyModuleController extends ControllerBase {

  /**
   * @return string[]
   */
  public function index() {
    return [
      '#markup' => 'Hello world ?',
    ];
  }

}

to read more about that topic see this link.