TwitterSignInView and associated viewmodel provide the UI for gathering the user’s Twitter credentials. The sample, however, does not require the user to sign in to Twitter, because we are merely retrieving the timeline for the user, and this does not require authentication.
A sign-in screen is included to provide the infrastructure to extend the app in the direction of being a fully blown Twitter app. It also provides a nice segue to demonstrate the custom
INavigationService, which is discussed later in the chapter.
TwitterSignInViewModel class contains properties for the user’s Twitter credentials and a property that causes the password to be retained by the app (see Listing 29.5 ...