❔ How does one hold a value in a private field in a controller?
e.g. you don't want to store things with just their ids in case you store book id 1234 and then accidentally retrieve that book when trying to get user id 1234
❔ How does one hold a value in a private field in a controller?
E.g. IGetBookFromDatabase would be the interface, GetBookFromSqlDatabase physically goes to the DB, CachedGetBookFromDatabase takes a cache and an IGetBookFromDatabase