The route

Inside our module, we will need to create our routing file that will hold all our statically defined routes. The name of this file will be hello_world.routing.yml. By now, I assume that you understand what the deal is with the file naming conventions in a Drupal 8 module. However, in any case, this is another YAML file in which we will need to put the YAML formatted data:

hello_world.hello:
  path: '/hello'
  defaults:
    _controller: '\Drupal\hello_world\Controller\HelloWorldController::helloWorld'
    _title: 'Our first route'
  requirements:
    _permission: 'access content'

This is our first route definition. It starts with the route name (hello_world.hello) followed by all the necessary info about it, below, in a YAML formatted multidimensional array. The standard practice is to have the route name start with the module name it is in, followed by route qualifiers as needed.

So, what does the route definition contain? There can be many options here, but, for now, we will stick with the simple ones that serve our purpose. For more info about all that you can configure, visit the relevant documentation page on https://www.drupal.org/docs/8/api/routing-system/structure-of-routes. It is a good resource to keep on hand.

First, we have a path key, which indicates the path we want this route to work on. Then, we have a defaults section, which usually contains info relevant to the handlers responsible for delivering something when this route is accessed. In our case, we set the controller and method responsible for delivering the page and the title of the page. Finally, we have a requirements section, which usually has to do with conditions that need to be met for this route to be accessible (or be hit)--things such as permissions and format. In our case, we will require users to have the access content permission, which most visitors will have. Don't worry, we will cover more about access in a later chapter.

That is all we need for our first route definition. Also, note that the Drupal 8 routing system is essentially identical to that of Symfony, albeit with some modifications here and there, and although our route definition is done, we will now need to create the Controller that maps to it and can deliver something to the user.

Before we do that, let's look at an example of a very common routing requirement you will most likely have to use really soon. We don't need this for the functionality we're building in this chapter, so I won't include it in the final code. However, it's important that you know how this works.