You have to pop the selected tab bar navigation stack to root.. You can achieve this by several method one is as below..
In your AppDelegate implement the tabbarcontroller delegate function, make sure you have set the tabbarcontroller delegate to AppDelegate..
-(void) tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
//Check the selected index to 0
if ([viewController isKindOfClass:[UINavigationController class]] && tabBarController.selectedIndex == 0) {
[(UINavigationController *)viewController popToRootViewControllerAnimated:NO];
}
}