solved
in my appDelegate didFinishLaunchingWithOptions i was using :
[self.window addSubview:myTabBar.view];
instead of
[self.window addSubview:myTabBar.view];
full source should look like :
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
...
self.window.rootViewController = myTabBar;
[self.window makeKeyAndVisible];
...
}