Question

In my app there is authentication required, so when you launch one of the tabs on tab bar, “class A” checks are there credentials saved if not, “class B” modal view controller with fields to login launches.

So my question is : in which method in class A (loadView, viewWillAppear or maybe in another one) should be implemented checking if there are credentials saved and other stuff described above.

And my additional second question is:
is pushing modalviewcontroller correct way to show login screen, or i should do that differently?

Thank you for reply guys.

OH ! One More Thinh

And one more thing. I’ve done implementing LoginView by adding delegate and presenting ModalVC (Harkonian the Piquant’s method). But in my tab bar app i have got very confusing problem. I mean when user taps login button (assume that everything was correct and he’s able to secured data) how PROPERLY switch to tab where is secured info. I mean previously selected tab.

i did it by adding in

-(IBAction) login {

//some code

self.tabBarController.selectedIndex =1;

And it seem to work good but is it correct ?

Answer 1

I have a very similar use case in my app — it requires a passcode to authenticate. After a lot of testing and tweaking I found the following design to be the best approach:

Don’t use class A to launch your credentials VC — use the app delegate instead.

For security purposes, typically you’ll want the credentials VC to show before the user can view the underlying view. It’s much easier to handle this in the app delegate than in a VC. In addition, you need to consider what happens when your app is backgrounded — a screen shot is taken of the current state of the app. If you are using viewController A to show the credentials view, when the app relaunches the user will be able to see whatever sensitive information was visible on app close until the app finishes launching and VC A presents the credentials VC.

Don’t insert your credentials view into an existing ViewController — use a new UIWindow instead.

You don’t ever want any other view to be able to sit on top of your credentials view. Ever. Even views that would normally always be on top, like UIAlertView. The easiest way to achieve this is to have a special UIWindow just for your credentials view. Show this window and hide the primary app window whenever you need to display the credentials view.

How does this approach look in practice?

If you are at all interested in how well this design works, you can check out the passcode feature in Audiotorium Notes for iPad. I spent a lot of time with this design to make sure it was as secure as possible.

If you have any specific implementation quests feel free to ask and I’ll try to answer them.