How to: Save order of tabs when customizing tabs in UITabBarController

As far as you've asked for some sample code I will simply post here how I dealt with the same task in my app.

Quick intro: I was using a NIB file for storing initial UITabBarController state and to differ my tabs one from another I simply defined tag variables for UITabBarItem objects assigned to each UIViewController stuffed in my UITabBarController. To be able to accurately track last selected tab (including the 'More' one) I've implemented following methods for UITabBarControllerDelegate of my UITabBarController and UINavigationControllerDelegate of its moreNavigationController. Here they are:

#pragma mark UINavigationControllerDelegate

- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
    [[NSUserDefaults standardUserDefaults] setInteger:mainTabBarController.selectedIndex forKey:@"mainTabBarControllerSelectedIndex"];
}

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
    [[NSUserDefaults standardUserDefaults] setInteger:mainTabBarController.selectedIndex forKey:@"mainTabBarControllerSelectedIndex"];
}

#pragma mark UITabBarControllerDelegate

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {
    [[NSUserDefaults standardUserDefaults] setInteger:tabBarController.selectedIndex forKey:@"mainTabBarControllerSelectedIndex"];
}

And here's the code for saving the tabs order:

#pragma mark UITabBarControllerDelegate

- (void)tabBarController:(UITabBarController *)tabBarController didEndCustomizingViewControllers:(NSArray *)viewControllers changed:(BOOL)changed {
    int count = mainTabBarController.viewControllers.count;
    NSMutableArray *savedTabsOrderArray = [[NSMutableArray alloc] initWithCapacity:count];
    for (int i = 0; i < count; i ++) {
        [savedTabsOrderArray addObject:[NSNumber numberWithInt:[[[mainTabBarController.viewControllers objectAtIndex:i] tabBarItem] tag]]];
    }
    [[NSUserDefaults standardUserDefaults] setObject:[NSArray arrayWithArray:savedTabsOrderArray] forKey:@"tabBarTabsOrder"];
    [savedTabsOrderArray release];
}

As you can see I've been storing the order of tabs' indexes in an array in NSUserDefaults.

On app's launch in applicationDidFinishLaunching: method I reordered the UIViewControllers using following code:

- (void)applicationDidFinishLaunching:(UIApplication *)application {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    mainTabBarController.delegate = self;

    int count = mainTabBarController.viewControllers.count;
    NSArray *savedTabsOrderArray = [[userDefaults arrayForKey:@"tabBarTabsOrder"] retain];
    if (savedTabsOrderArray.count == count) {
        BOOL needsReordering = NO;

        NSMutableDictionary *tabsOrderDictionary = [[NSMutableDictionary alloc] initWithCapacity:count];
        for (int i = 0; i < count; i ++) {
            NSNumber *tag = [[NSNumber alloc] initWithInt:[[[mainTabBarController.viewControllers objectAtIndex:i] tabBarItem] tag]];
            [tabsOrderDictionary setObject:[NSNumber numberWithInt:i] forKey:[tag stringValue]];

        if (!needsReordering && ![(NSNumber *)[savedTabsOrderArray objectAtIndex:i] isEqualToNumber:tag]) {
                needsReordering = YES;
            }
        }

        if (needsReordering) {
            NSMutableArray *tabsViewControllers = [[NSMutableArray alloc] initWithCapacity:count];
            for (int i = 0; i < count; i ++) {
                [tabsViewControllers addObject:[mainTabBarController.viewControllers objectAtIndex:
                                                [(NSNumber *)[tabsOrderDictionary objectForKey:
                                                              [(NSNumber *)[savedTabsOrderArray objectAtIndex:i] stringValue]] intValue]]];
            }
            [tabsOrderDictionary release];

            mainTabBarController.viewControllers = [NSArray arrayWithArray:tabsViewControllers];
            [tabsViewControllers release];
        }
    }
    [savedTabsOrderArray release];

    if ([userDefaults integerForKey:@"mainTabBarControllerSelectedIndex"]) {
        if ([userDefaults integerForKey:@"mainTabBarControllerSelectedIndex"] == 2147483647) {
            mainTabBarController.selectedViewController = mainTabBarController.moreNavigationController;
        }
        else {
            mainTabBarController.selectedIndex = [userDefaults integerForKey:@"mainTabBarControllerSelectedIndex"];
        }
    }

    mainTabBarController.moreNavigationController.delegate = self;

    [window addSubview:mainTabBarController.view];
}

It's quite tricky and may seem strange, but don't forget that my UITabBarController was fully created in a nib file. If you construct it programmatically you may simply do the same but following the saved order.

P.S.: and don't forget to synchronize NSUserDefaults when your app terminates.

- (void)applicationWillTerminate:(UIApplication *)application {
    [[NSUserDefaults standardUserDefaults] synchronize];
}

I hope this will help. If something is not clear please do comment and ask.

First I voted up the previous answer, but then I noticed how ridiculously complex it is. It can and should be simplified.

- (void)applicationDidFinishLaunching:(UIApplication *)application {

    NSArray *initialViewControllers = [NSArray arrayWithArray:self.tabBarController.viewControllers];
    NSArray *tabBarOrder = [[AppDelegate sharedSettingsService] tabBarOrder];
    if (tabBarOrder) {
        NSMutableArray *newViewControllers = [NSMutableArray arrayWithCapacity:initialViewControllers.count];
        for (NSNumber *tabBarNumber in tabBarOrder) {
            NSUInteger tabBarIndex = [tabBarNumber unsignedIntegerValue];
            [newViewControllers addObject:[initialViewControllers objectAtIndex:tabBarIndex]];
        }
        self.tabBarController.viewControllers = newViewControllers;
    }

    NSInteger tabBarSelectedIndex = [[AppDelegate sharedSettingsService] tabBarSelectedIndex];
    if (NSIntegerMax == tabBarSelectedIndex) {
        self.tabBarController.selectedViewController = self.tabBarController.moreNavigationController;
    } else {
        self.tabBarController.selectedIndex = tabBarSelectedIndex;
    }

    /* Add the tab bar controller's current view as a subview of the window. */
    [self.window addSubview:self.tabBarController.view];
}

- (void)applicationWillTerminate:(UIApplication *)application {

    NSInteger tabBarSelectedIndex = self.tabBarController.selectedIndex;
    [[AppDelegate sharedSettingsService] setTabBarSelectedIndex:tabBarSelectedIndex];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

- (void)tabBarController:(UITabBarController *)tabBarController didEndCustomizingViewControllers:(NSArray *)viewControllers changed:(BOOL)changed {

        NSUInteger count = tabBarController.viewControllers.count;
        NSMutableArray *tabOrderArray = [[NSMutableArray alloc] initWithCapacity:count];
        for (UIViewController *viewController in viewControllers) {

            NSInteger tag = viewController.tabBarItem.tag;
            [tabOrderArray addObject:[NSNumber numberWithInteger:tag]];
        }

        [[AppDelegate sharedSettingsService] setTabBarOrder:[NSArray arrayWithArray:tabOrderArray]];
        [tabOrderArray release];
    }

All this happens in AppDelegate. You set UITabBarController's delegate to AppDelegate instance in Interface Builder. sharedSettingsService is what persists the data for me. Basically it can be a NSUserDefaults front-end or anything you like (CoreData for example). So everything is simple, Interface Builder helps here, not makes things more complex.