If you want to create a link to a internal page in a Twig template, and there's not already a variable in the template that contains the URL you want to link to, you'll need to determine the route of the thing you want to link to and then use the Twig
path() functions to generate appropriate URLs. In most cases when you want to create a link to an entity that is being output by the current template there's an existing helper variable to use.
When a user visits a particular URL on a Drupal site, the path they are visiting is a route. Drupal's routing system helps figure out which controller is responsible for responding to the route being requested. Drupal matches the incoming request's path to a controller by looking through the routes that have been registered in active modules.
- Create your own routes in custom modules
- Understand how Drupal's routing system maps paths to controllers
At this point in the development cycle of Drupal the routing system is relatively stable. This is mainly because Drupal's routing system leverages the Symfony routing component. Resources labeled with Drupal 8 should also apply to Drupal 9.
This tutorial walks through the process of creating a custom content entity. Since there are several url paths that will display various types of information about our custom entity there are multiple examples of registering routes in this tutorial as well.