Login/Logout screen for existing iphone app (Swift/Storyboard)

We have an existing iphone app in Swift with a storyboard which needs a clean login screen added at app startup. We have a RestApi for the access token of login which is generated with Microsofts .Net framework in C#. We will provide the url link for sending the username/email and password, a token will come back, the token needs to be saved in ios user session. suggest using singleton pattern. We will provide existing iphone app with a test username/password on bitbucket Basic Flow: On app startup, check for valid token (make sure not expired) Show user welcome page if valid Show Login screen if not valid or not existing Display Login fail message if failed Display User welcome page if succeed Simple link for "Forgot Password" which allows input of email, link sent to restApi. Return user to login screen with message "check your email" No need for register page Requirements: Swift IOS developer Understanding of .Net Token based auth http://www.asp.net/web-api/overview/security/individual-accounts-in-web-api Some basic design skill for making a decent login screen