Problems calling instance method

Following code changes tab name and select then index 2.

[(UITabBarItem*)[self.rootController.tabBar.items objectAtIndex:0] setTitle:@"User"];

self.rootController.selectedIndex = 2;

However, it works for example when app didFinishLaunching method but not working when called like follows.

touch up inside button triggers renameTabs:

- (IBAction) renameTabs: (id)sender
{
    CompanyAppDelegate *theInstance = [[CompanyAppDelegate alloc] init];
    [theInstance rename];

}

and in the controller:

- (void) rename
    {

        [(UITabBarItem*)[self.rootController.tabBar.items objectAtIndex:0] setTitle:@"User"];

        self.rootController.selectedIndex = 2;

    }

rename function is triggered and al开发者_开发技巧so defined at .h. No errors but nothing changes! Is there anything wrong?? Thank you

You shouldn't create new CompanyAppDelegate. Try to implement method sharedAppDelegate in CompanyAppDelegate.m:

+ (CompanyAppDelegate *)sharedAppDelegate
{
    return (CompanyAppDelegate *) [UIApplication sharedApplication].delegate;
}

Don't forget to declare it in CompanyAppDelegate.h.

And replace renameTabs with this one:

- (IBAction) renameTabs: (id)sender
{
    CompanyAppDelegate *theInstance = [CompanyAppDelegate sharedAppDelegate];
    [theInstance rename];
}

- (IBAction) renameTabs: (id)sender
{
    CompanyAppDelegate *theInstance = (CompanyAppDelegate *) [UIApplication sharedApplication].delegate;
    [theInstance rename];

}

- (void) rename
    {

        [(UITabBarItem*)[self.rootController.tabBar.items objectAtIndex:0] setTitle:@"User"];

        self.rootController.selectedIndex = 2;

    }

[Ah, when I first read this I thought you said rename wasn't reached. Never mind.]