We saw how we can expose to Views our own data that is totally custom. However, we can also alter existing data definitions provided by Drupal core or other modules by implementing hook_views_data_alter(). The $data parameter passed by the reference will contain everything that has been defined and can be changed as needed.
Moreover, we can also use this implementation to create some new Views fields or filters on other tables that do not "belong" to us. This is actually more common than exposing totally custom tables or other kinds of resources. For example, we may want to create a new Views field that shows something related to the Node in the results. So, let's look at an example.
Do you remember in Chapter 6 , Data ...
