Drupal 8 Module Development

Cache contexts

Once we thought about the dependencies of the render array, the second most important thing to consider is what it differs by. In other words, is there any reason why this render array should be shown one way sometimes but another way some other time?

Let's take a simple example of a render array that prints out the name of the current user. Nothing could be less complicated. Ignoring the cache tags for now, we immediately realize that we cannot show the same username to all users, right? So, the user Danny should see "Hi Danny" while user John should see "Hi John". We are talking about the same render array but one that differs by context. In other words, a variation of this render array needs to get cached separately for ...