Getting the selectedIndex of the currently selected tab from a viewcontroller

[mensch]

I'm developing an iPhone application with a tabbar and multiple viewcontrollers. I'm a novice concerning the iPhone and the SDK, so bear with me.

I'd like to get the selectedIndex of the tabbar from my viewcontroller. But no matter what I try to do, it returns (null) and the application crashes as soon as I switch to another tab section.

I tried calling the following in my FirstViewController.m:

MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
  NSLog(@"%@", appDelegate.tabBarController.selectedIndex);

and:

NSLog(@"%@", self.tabBarController.selectedIndex);

But all return (null).

How would I do this correctly? The code for my viewcontroller and appdelegate follows. All the views are designed in Interface Builder.

MyAppDelegate.h

#import <UIKit/UIKit.h>

@interface MyAppDelegate : NSObject <UIApplicationDelegate, UITabBarControllerDelegate> {
  UIWindow *window;
  UITabBarController *tabBarController;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UITabBarController *tabBarController;

@end

MyAppDelegate.m

#import "MyAppDelegate.h"

@implementation MyAppDelegate

@synthesize window, tabBarController;

- (void)applicationDidFinishLaunching:(UIApplication *)application {
  [window addSubview:tabBarController.view];
}

- (void)dealloc {
    [tabBarController release];
    [window release];
    [super dealloc];
}

@end

FirstViewController.h

#import <UIKit/UIKit.h>

<UITableViewDataSource, UITableViewDelegate> {
@interface FirstViewController : UITableViewController {
}

@end

FirstViewController.m

#import "FirstViewController.h"

@implementation FirstViewController

- (void)viewDidLoad {
  [super viewDidLoad];
  self.title=@"Agenda";
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
}

- (void)dealloc { 
	[super dealloc];
}

[BrianSlick]

%d, not %@

[mensch]

Ouch, that's obvious. I could have sworn I already used %d instead of %@ while testing.

Calling it like in viewDidLoad in FirstViewController.m returns the correct index:

MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];
  NSLog(@"%d", appDelegate.tabBarController.selectedIndex);

The only problem I now have is that it returns the value only once. My guess is that that's because the view has already been loaded before. Is there a way to work around this?

[BrianSlick]

viewWillAppear

[mensch]

Great! Thanks, that did the trick.