Block access
Another major area where you will deal with access is when trying to control access to a custom block. If you remember in Chapter 2, Creating Your First Module, we created the HelloWorldSalutationBlock plugin so that our salutation can also be rendered using a block. Now, that block can be placed in a region and even configured to show up only on certain pages, for certain user roles, or even on node pages restricted by bundle. This is all done in the UI:
However, this is oftentimes not enough, and you will want to have a block placed in a region and control yourself under what circumstances it should show up--enter block access.
Inside the BlockBase plugin base class, there is the blockAccess() method, which always returns positively. This is because, by default, all blocks will be rendered--once they are placed in a region. Unless, of course, they are configured to only show in certain cases, in which case a system of visibility based on the available contexts kicks in to control...
