Summary

In this chapter, we covered a great deal of info about the things you need to know when developing Drupal 9 modules. The first thing we did was create our very own module skeleton that can be installed on a Drupal site. Then, we saw how to create a new page at a specific path (route) and show some basic data on that page. Nothing too complex, but enough to illustrate one of the most common tasks you will do as a module developer. We then took that to a new level and abstracted the logic for that data calculation into a service. Not only that, but we also saw how we can use that service and, more importantly, how we should use it. Next, we saw how we can work with the Form API to allow administrators to add some configuration to the site. Also, since we talked about forms, we saw how we can alter existing ones defined by other modules—a useful technique for any module developer.

Next, we created our first custom block, which allowed us to reuse our service and be more flexible with where we show our data.

Then, we looked at how to create URLs and links programmatically. In the functionality we built in this module, we don't need any links, yet. However, it is common practice to work with them, so we had to learn early how to generate links and work with URLs properly in Drupal.

In the last section, we explored the Symfony Event Dispatcher component, something that allows us to dispatch and subscribe to events. We saw some examples of how we can subscribe to one of the main Kernel events in order to redirect the page, but we also saw how to dispatch our own event. The latter was meant to allow subscribers to make changes to our data.

Most of the topics we covered in this chapter were meant to give you an initial boost and the tools to start developing modules in Drupal 9. They represent the absolute most common things—I believe—that any new Drupal developer encounters and has to do.

In the next chapter, we will look at two important aspects most applications will need to use. One is logging—the better your site logs its errors and important actions, the easier it will be to debug and trace back issues. Another is mailing. Websites usually need to send out emails to users in one way or another, so it's important that we see how that works in Drupal 9.