On clicking a tab need to answer an alert before moving into the tab clicked - iPad programming - objective-c

Question

There are many tabs in my screen,I want to give an alert box which says "Do you want to save the changes?" if user changes anything in the page, without clicking on the save button provided in the page,he is clicking on diff tab.
I'm able to get the alert view but the tab click moves the screen to the tab which was clicked. The screen should not change until the alert view is answered.
Can anyone let me know how to suppress the screen change until the alert view is answered ?

Answer 1

This doesn't directly answer your question, but: what you're trying to do sounds like bad UI design. (In general, if it feels like you are fighting against UIKit, you're probably doing it the wrong.)
In this case: if you really want to ensure that a user taps a Save button before moving to a different screen, you should present that screen in a modal view, so that it is impossible to navigate to any other part of the app.
In other words, if you want to prevent a user from navigating away from a screen, don't show them buttons or tabs that would allow them to navigate away. Otherwise, you're just making more work for yourself and frustrating a user.

Answer 2

Implement UITabBarControllerDelegate in your app delegate's applicationDidFinishLaunching
- (void)applicationDidFinishLaunching:(UIApplication *)application
{
self.tabBarController.delegate = self;
[window addSubview:self.tabBarController.view];
}
Then use the below delegate method,
- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController;
This method is called before the tab switch and you can return no here to disable that and show an alert message instead. Once the user has performed the save either he can press on tab again or you can programmatically switch to the new tab as,
self.tabBarController.selectedViewController = [self.tabBarController.viewControllers objectAtIndex:0];
Add this inside your delegate,
How about this for switching to the tab programmatically,
- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController {
if () {
//some code
} else {
//some other code
self.tabBarController.selectedViewController = viewController;
}
}