How to implement an iOS login screen that only appears for unauthenticated users

Question

I know this question is a bit open-ended but I'm trying to make it as specific as possible because I don't really know what a standard convention would be for this type of thing with iOS. I have been looking into implementing a login screen on my app, however I am having trouble figuring out the best way. I have three methods listed below, could anybody tell me if one of these is better or a more correct approach? (or if there is something that I totally missed).

The first approach - I initially have a navigation controller as my root controller with the login screen being the first view on the stack. Then when the user logs in, i just push the main UI to the stack. The user can then use the back button to return to the login screen. I know this technique works but then when re-launching the app, the user doesn't need to login again. I'm not sure should I just set up the stack the same way (login page first) and then push the main UI on top? Is that a common technique?

The next approach, I found here how to replace the root controller How to change RootViewController (in AppDelegate) from within CustomViewController? I like this idea better where I could just get rid of the login screen after login and add some type of button to bring it back on logout. Then during re-launch I can just skip adding the login screen altogether.

The third approach is perhaps overlaying the login on top of the main UI but I haven't found any code to do this. It also seems a little weird because my main UI might start firing messages that i wouldn't want to occur until after login so I'd have to account for that.

Answer 1

I would suggest you to have a root view controller with a blank view. This controller is set as a root view controller in the AppDelegate's applicationDidFinishLaunching: method.

Role of this root view controller would be to show the login screen through login view controller initially. Login view controller delegates to root view controller upon successful login to remove itself from root view and root view controller then set the next controller to be displayed.

This way you can manages multiple views if any before showing the main view through your root view controller.

There are different ways to display login view on top of root view.

1) Present a login view controller without animation.

2) Add login view as a subview on top of root view [Note: Before iOS 5, you don't get the rotation and view life cycle call backs and you should write your own code to pass the callbacks to the view added on top of root view. From iOS 5 onwards you have view containment concept using which you can maintain parent child relationship.]

Hope this helps.

Answer 2

We have a similar app. Our storyboard looks a little like a wheel.

We have a navigation controller as our root controller, which then goes to a view controller with a spinner on it. That controller handles the call to see if the user is logged in or not. It is connected to two different controllers.

If they are already logged in, it goes to the main view controller. If they haven't logged in, it goes to the login view controller. The login view controller will go back to initial view controller on success, and since they'll then be logged in, it goes to the main controller.

To fall back, we go all the way back to the initial view controller with the spinner on it.

You can hide the navigation bar on every view before the main one.

Answer 3

All our ViewController are subclassed from a custom subclass of uiviewcontroller. This allow us to make powerful enhancements on behavior, constraints, ...

Our super view controller class handle authentification by summoning a modal view on viewWillAppear if user is not logged in. Works like a charm to handle disconnection and resuming from any point in the app.

Answer 4

I always implement it with storyboard. Just add Storyboard ID to your login view controller, say Onboarding .

Then write something like this in application: didFinishLaunchingWithOptions:

if (![[NSUserDefaults standardUserDefaults] objectForKey:TRAIN_COMPLETE]) {
    UIStoryboard* storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    self.window.rootViewController = [storyboard instantiateViewControllerWithIdentifier:@"Onboarding"];
}