Question

I currently encountering a problem with my iOS application.
I am attempting to incorporate a gradual login pattern, i.e.: the use can access some of the app without being required to login.

Required features are as follows:

• At all times the user can view all navigation items that require login
• When the user attempts to access an uiview(controller) that requires login, they will be prompted with a UIAlertView asking them to log in. (Preferably the UIAlertView will appear when the app recognised the initiated segue destination is restricted).

At first I used a subclass of UIViewController that, in the designated initialiser (initWithCoder), would check NSUserDefaults to see if the user was logged in. I then subclassed off of that. Limitations were as follows:

• Couldn’t use other subclasses of UIViewController, namely UITableViewController
• The UIAlertView came up after the view had appeared, which i am assuming would cause errors if the subclassed UIViewController assumed the user was logged in.

Question summary:
I would like to know how to conditionally prevent users from accessing certain UIView(Controller)s and subclasses of UIViewController, and when that happens present a UIAlertView.

Update 1
Could categories and/or protocols be a viable solution?

Update 2
CodaFi pointed out singletons as a great solution to manage the user’s state.

With that implemented I now need to figure out how to control the user’s access.
As I am using storyboards I feel that the most versatile implementation would be subclassing UIStoryboardSegue, and on the perform method check if the user is attempting to access an restricted UIViewController (perhaps restricted controllers have a protocol property that specifies the required status: logged in/out). However the pitfall here is that you cannot choose the class/subclass of a UIStoryboardSegue in the storyboard graphic editor. I am aware that I could do it programatically, however that seems tedious as i would have to add IBActions and like that to methods that perform segues, furthermore I don’t think that would work with the way elements such as navigationController and tabbarControllers behave.

Does anybody have a viable solution to restricting the user’s navigation?

Update 3
I’ve added an answer to this question, however I still deem it as unanswered because the answer I’ve written doesn’t take into account segues between navigation bar controllers. However it may help some people.

Answer 1

So, I’ve answered how to do this using custom segues.

Now I understand my real problem was the mental disconnect with the tabbarcontrollerdelegate protocol.

As a solution to preventing access to tabs I’ve made a class to handle said tab bar controller

#import <Foundation/Foundation.h>

@interface TabBarDelegate : NSObject<UITabBarControllerDelegate,UIAlertViewDelegate>{
    UITabBarController *cachedTabBarController;
}

@end

#import "TabBarDelegate.h"

@implementation TabBarDelegate

-(BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController{
    NSLog(@"%s",__FUNCTION__);
    NSLog(@"Pretending the user isnt logged in");

    if(true){
        NSString *message = [NSString stringWithFormat:@"You require an account to access %@",viewController.tabBarItem.title];
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Account Required" message:message delegate:self cancelButtonTitle:@"Okay" otherButtonTitles: @"Login",@"Create Account",nil];
        [alert show];
        //Hold tabbarcontroller property for alert callback
        cachedTabBarController = tabBarController;
        return false;
    }

    return true;
}

-(void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex{
    if(cachedTabBarController){
        switch (buttonIndex) {
            case 1:
                //Login
                [cachedTabBarController performSegueWithIdentifier:@"tabBarToLogin" sender:cachedTabBarController];
                break;
            case 2:
                //Sign up
                [cachedTabBarController performSegueWithIdentifier:@"tabBarToSignup" sender:cachedTabBarController];
                break;
            default:
                break;
        }
        //Release tab bar controller from memory
        cachedTabBarController = nil;
    }
}

@end

Then i wired it up to my appDelegate in applicationDidFinishLaunching…

//Hook up tab bar delegate
    mainTabController = (UITabBarController*)self.window.rootViewController;
    mainTabBarDelegate = [[TabBarDelegate alloc] init];
    mainTabController.delegate = mainTabBarDelegate;

And Voila