Correct flow to log in user from iOS app to remote API

Question

Here's the logic flow I'm trying to code into my iPhone app:

I think I understand the technicalities to achieve this (using AFNetworking, connecting to a Rails API using Devise as authentication). The auth_token will be stored in the keychain once the login is successful. What I can't figure out is the best way to go about setting up my app to behave like above.

I want the experience to be good for the user of course, so maybe while it's checking for the token and attempting to login it shows a "loading" screen of some sort.

How would I go about achieving this? I don't know which view controller I should set as the rootviewcontroller in the AppDelegate or how I should set it after the user has logged in. I've tried this in the Facebook app and when I open it I see a blank navigation controller it seems, then my profile view is loaded. What are they doing behind the scenes and is this the best way to go?

I am not using Storyboards.

Answer 1

I have implemented a similar one, the RootViewController was a "SplashViewController" in a navigationController, showing a nice logo, activity indicator and gives user info about authentication status. It holds the logic for checking stored token there and authentication implementation. If authentication is successfull, ShowUserController is shown by pushing to navigationController stack.

If authentication is failure a LoginViewController is presented modally. SplashViewController implements the delegate of LoginViewController, which does nothing but passing the username and password to SplashViewController. On successfull login, LoginViewController is dismissed and user is directed to ShowUserController.

Answer 2

Start your app with the root controller as the one that the user will see after they have logged in successfully, then layer the login views/controllers on top, with modal calls. If the authentication is successful, your user will already be where they want to be, else you call the login layers modally on top. Once they're authenticated, you won't need the login views anymore.