iPhone loading screen until web request is finished - objective-c

Question

I need to show "Loading screen" (just an image) at the start of application and when application gets all needed data from web, then first viewcontroller is shown. I have succeded doing it by setting my own black screen "Default.png" as "LoadingScreen.png" (Of course named again as Default.png) and
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
self.viewController = [[THWViewController alloc] initWithNibName:#"THWViewController" bundle:nil];
[self performSelector:#selector(start) withObject:nil afterDelay:5.0];
[self.window makeKeyAndVisible];
return YES;
}
- (void)start
{
self.window.rootViewController = self.viewController;
}
I would change that random delay to when api loading is finished, but is this a good way of implementing it ? Because i get that message that rootviewcontroller is expected.

Answer 1

You might want to consider using a block so you can eliminate that random delay. I would also consider calling this from your first view rather than starting with no root (remove the warning):
//show your loading screen over your first view
dispatch_async( dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Get all the needed data
dispatch_async( dispatch_get_main_queue(), ^{
// do what you need to do with data and in first view
//hide the loading screen
});
});