GameCenter showing Leaderboard in another Scene - ios

Question

I enabled Game Center functionality in my SpriteKit game in the ViewController. Everything works fine, but I want to show the Leaderboard in another Scene after a Button is touched. I imported everything correctly. My project crashes now after touching the 'HighScoreButton' in the Head.m file, with following Output:
'NSInvalidArgumentException', reason: '-[UIView presentScene:]: unrecognized selector sent to instance 0x7feec2ff2920'
My recent Code that doesn't work:
ViewController.h
#interface ViewController : UIViewController <GKGameCenterControllerDelegate>
- (void)showLeaderboardAndAchievements:(BOOL)shouldShowLeaderboard;
+ (ViewController*)defaultHelper;
#end
ViewController.m
- (void)viewDidLoad
{
[super viewDidLoad];
// Configure the view.
SKView * skView = (SKView *)self.view;
[self authenticateLocalPlayer];
// Create and configure the scene.
SKScene * scene = [Head sceneWithSize:skView.bounds.size];
scene.scaleMode = SKSceneScaleModeAspectFill;
self.canDisplayBannerAds = YES;
// Present the scene.
[skView presentScene:scene];
}
static ViewController *_sharedHelper = nil;
+ (ViewController*)defaultHelper {
// dispatch_once will ensure that the method is only called once (thread-safe)
static dispatch_once_t pred = 0;
dispatch_once(&pred, ^{
_sharedHelper = [[ViewController alloc] init];
});
return _sharedHelper;
}
-(void)showLeaderboardAndAchievements:(BOOL)shouldShowLeaderboard{
GKGameCenterViewController *gcViewController = [[GKGameCenterViewController alloc] init];
gcViewController.gameCenterDelegate = self;
if (shouldShowLeaderboard) {
gcViewController.viewState = GKGameCenterViewControllerStateLeaderboards;
gcViewController.leaderboardIdentifier = _leaderboardIdentifier;
}
else{
gcViewController.viewState = GKGameCenterViewControllerStateAchievements;
}
[self presentViewController:gcViewController animated:YES completion:nil];
}
-(void)gameCenterViewControllerDidFinish:(GKGameCenterViewController *)gameCenterViewController
{
[gameCenterViewController dismissViewControllerAnimated:YES completion:nil];
}
Head.m
if ([Node.name isEqualToString:#"HighScoreButton"]){
[[ViewController defaultHelper] showLeaderboardAndAchievements:YES];
}

Answer 1

I believe the problem is with the singleton initialization of your view controller (which is correct btw).
When first loaded the view controller is created "behind the scenes" (I am not sure where exactly but I'll look for it) and its view is initialized with an skView instance. (And since it is not created by you your singleton instance is not initialized and a different ViewController instance is used)
Since your defaultHelper method is not used on the first creation of your view controller you are creating a new view controller which its view is an instance of UIView and it does not comply to the SKView methods (such as setShowFPS and presentScene). And of course since you create a new view controller it is not part of the view hierarchy.
What I recommend for you is to retrieve the view controller as follows :
if ([Node.name isEqualToString:#"HighScoreButton"]){
ViewController *viewController = self.view.window.rootViewController;
[viewController showLeaderboardAndAchievements:YES];
}