Authenticating the local player - Game Center - iOS6 - authentication

Question

I'm completely new to development in Game Center. I have watched the videos in WWDC and looked at the developer website. They suggest I enter code like this for iOS 6:
- (void) authenticateLocalPlayer
{
GKLocalPlayer *localPlayer = [GKLocalPlayer localPlayer];
localPlayer.authenticateHandler = ^(UIViewController *viewController, NSError *error){
if (viewController != nil)
{
[self showAuthenticationDialogWhenReasonable: viewController
}
else if (localPlayer.isAuthenticated)
{
[self authenticatedPlayer: localPlayer];
}
else
{
[self disableGameCenter];
}
}];
}
I have copied this into the app delegate.m file, however it does not like it, showing errors like expecting a ] after [self showAuthenticationDialogWhenReasonable: viewController
} amongst others.
Can anyone please tell me how to authenticate the user for game center in iOS 6?

Answer 1

To get an introduction to GameKit, there are samples available from apple, for example:
https://developer.apple.com/library/ios/#samplecode/GKLeaderboards/Introduction/Intro.html.
In your code you are missing the closing "]", but of course you need more than just this function to connect to the gameCenter. Best start with one of the samples.

Answer 2

Apple has posted incorrect code, the ]; towards the end of the code belongs at the end of this line [self showAuthenticationDialogWhenReasonable: viewController
this code is not needed because this is just explaining how the method authenticateLocalPlayer works inside of Gamekit

Answer 3

Here's what I did without having to use the deprecated methods:
Set the authentication handler immediately in the AppDelegate by calling the function below (I put it in a singleton helper object). At this time, there is no view controller from which to show the login view controller, so if authentication fails, and the handler gives you a view controller, just save it away. This is the case when the user is not logged in.
- (void)authenticateLocalUserNoViewController {
NSLog(#"Trying to authenticate local user . . .");
GKLocalPlayer *_localPlayer = [GKLocalPlayer localPlayer];
__weak GKLocalPlayer *localPlayer = _localPlayer; // Avoid retain cycle inside block
__weak GCHelper *weakself = self;
self.authenticationViewController = nil;
localPlayer.authenticateHandler = ^(UIViewController *viewController, NSError *error)
{
if (viewController) {
NSLog(#"User not logged in");
weakself.authenticationViewController = viewController; // save it away
} else if (localPlayer.authenticated) {
[[GKLocalPlayer localPlayer] unregisterListener:self];
[[GKLocalPlayer localPlayer] registerListener:self];
NSLog(#"Local player %# (%#) authenticated. ID = %#",localPlayer.alias, localPlayer.displayName, localPlayer.playerID);
} else {
// Probably user cancelled the login dialog
NSLog(#"Problem authenticating %#", [error localizedDescription]);
}
};
}
Then, once your main screen has loaded, and the user wants to press a button the start an online game, present the login view controller that you stashed away earlier. I put this in another method in my helper class. When the user logs in, it will trigger an execution of your original authentication block, but the viewcontroller parameter will be nil.
-(BOOL) showGameCenterLoginController:(UIViewController *)presentingViewController {
if (self.authenticationViewController) {
[presentingViewController presentViewController:self.authenticationViewController animated:YES completion:^{
}];
return YES;
} else {
NSLog(#"Can't show game center view controller!");
return NO; // Show some other error dialog like "Game Center not available"
}
}