Revisiting the Singleton pattern
The Singleton pattern is obsolete, goes against the SOLID principles, and we replace it with a lifetime, as we’ve already seen. This section explores that lifetime and recreates the good old application state, which turns out to be nothing more than a singleton scoped dictionary.
We explore two examples here: one about the application state, in case you were wondering where that feature disappeared to. Then, the Wishlist project also uses the singleton lifetime to provide an application-level feature. There are also a few unit tests to play with the testability and to allow safe refactoring.
Project – Application state
You might remember the application state if you programmed ASP.NET using .NET Framework or the “good” old classic ASP with VBScript. If you don’t, the application state was a key/value dictionary that allowed you to store data globally in your application, shared between all sessions and...
