We've seen so far how to create access rules on our own routes. However, it would not be Drupal if it wasn't also easy to alter existing routes and change their access rules to whatever we want. This is yet another small extension point with which our custom modules can contribute to an existing functionality.
Altering route access is done by altering the routes themselves. Of course, access is not the only reason why routes may be altered, as you can change just about anything else on the definition. So, with this occasion, we will see how you can alter routes for any purpose you might need.
Routes can be altered by subscribing to an event, just as we've seen in Chapter 2, Creating Your First Module, when we subscribed to ...
