GameCenter Manager helps you manage Game Center in your iOS or Mac app. It makes it easy to report and keep track of high scores achievements, and challenges for different players. GameCenter Manager also takes care of the heavy lifting - checking internet availability, saving data when offline and uploading it when online, etc. In future updates, GameCenter Manager will make it easy to setup and run live Game Center Multiplayer matches.

1. Add the GameKit and SystemConfiguration frameworks to your Xcode project

2. Add the following classes (can be found in the GC Manager folder) to your Xcode project (make sure to select Copy Items in the dialog):

   • GameCenterManager (GameCenterManager-Mac on OS X)
   • Reachability
   • NSDataAES256

3. Open the GameCenterManager.h (GameCenterManager-Mac.h on OS X) file and change the kGameCenterManagerKey constant to the secret key you want to use for encryption/decryption

4. Import the GameCenterManager.h file (GameCenterManager-Mac.h on OS X)

5. Initialize GameCenter Manager and begin Syncing by using the following method call (preferrably in your appDidFinishLaunching method of your AppDelegate):

    [[GameCenterManager sharedManager] initGameCenter];
   

6. Add the delegate GameCenterManagerDelegate to your header file, then set the delegate in your implementation and add any delegate methods you'd like to use (see Delegates):

    [[GameCenterManager sharedManager] setDelegate:self];
   

GameCenter Manager's demo app makes it easier to test Game Center integration with GameCenter Manager on both Mac and iOS. It also lays out how to use the GameCenterManager class. We recommend that you leave the Bundle ID provided with the Demo App as-is. This Bundle ID is already linked to a Game Center game in iTunes Connect with scores and achievements. You may, however, substitute your own Bundle ID and entitlements file.

All methods, properties, types, and delegate methods available on the GameCenterManager class are documented below. If you're using Xcode 5 with GameCenterManager, documentation is available directly within Xcode (just Option-Click any method for Quick Help).

###Initialize GameCenterManager You should initialize GameCenterManager when your app is launched, preferably in the application didFinishLaunchingWithOptions method.

[[GameCenterManager sharedManager] initGameCenter];  

This checks if Game Center is supported in the current device, authenticates the player and synchronizes scores and achievements from Game Center if its being run for the first time.

###Check Game Center Support GameCenter Manager automatically checks if Game Center is available before performing any Game Center-related operations. You can also check for Game Center availability by using the following method, which returns a BOOL value (YES / NO).

BOOL isAvailable = [[GameCenterManager sharedManager] checkGameCenterAvailability];  

This method will perform the following checks in the following order: 1. Current OS version new enough to run Game Center. iOS 4.1 or OS X 10.8. Some Game Center methods require newer OS versions which will be checked (ex. challenges and some multiplayer features).
2. GameKit API availability. The GKLocalPlayer class must be available at a minimum.
3. Internet Connection. The Reachability class is used to determine if there is an active internet connection. GameCenterManager will still work without internet, however all saved data can only be uploaded with an internet connection.
4. Local Player. Check to make sure a local player is logged in and authenticated.

This method may return NO in many cases. Use the gameCenterManager: availabilityChanged: delegate method to get an NSDictionary containing information about why Game Center is or isn't available. Refer to the section on delegate methods below.

###Report Score Report a score to Game Center using a Game Center Leaderboard ID. The score is saved locally then uploaded to Game Center (if Game Center is available).

[[GameCenterManager sharedManager] saveAndReportScore:1000 leaderboard:@"Leaderboard ID"  sortOrder:GameCenterSortOrder];  

Set the Game Center Sort Order (either GameCenterSortOrderHighToLow or GameCenterSortOrderLowToHigh) to report a score to Game Center only if the new score is better than the best one (depending on the sort order). There is no need for you to find out if a user has beat their highscore before submitting it - GameCenterManager will determine if the score should be submitted based on the parameters provided.

###Report Achievement Report an achievement to Game Center using a Game Center Achievement ID. The achievement and its percent complete are saved locally then uploaded to Game Center (if Game Center is available).

[[GameCenterManager sharedManager] saveAndReportAchievement:@"Achievement ID" percentComplete:50];  

The percentComplete parameter specifies how much progress the user has made on an achievement. Specifiying a value of 100 will mark the achievement as completed. Values submitted between 1-99 will display in Game Center and show the user that they need to make more progress to earn an achievement. if you specify an achievement percent complete lower than the current percent complete, it will be ignored by Game Center.

###Get High Scores You can get high scores from multiple leaderboards or just one leaderboard. In both cases you'll need to provide Leaderboard IDs. GameCenterManager will return either an NSDictionary with integer scores, or one integer score. To get the high scores for the current player from multiple leaderboards:

// Array of leaderboard ID's to get high scores for
NSArray *leaderboardIDs = [NSArray arrayWithObjects:@"Leaderboard1", @"Leaderboard2", nil];

// Returns a dictionary with leaderboard ID's as keys and high scores as values
NSDictionary *highScores = [[GameCenterManager sharedManager] highScoreForLeaderboards:leaderboardIDs];  

To get the high score for the current player for a single leaderboard:

// Returns an integer value as a high scores
int highScore = [[GameCenterManager sharedManager] highScoreForLeaderboard:@"LeaderboardID"];  

###Get Achievement Progress You can get achievement progress for multiple achievements or just one achievement. In both cases you'll need to provide Achievement IDs. GameCenterManager will return either an NSDictionary with double values, or one double value. To get the achievement progress for the current player from multiple achievements:

// Array of achievement ID's to get progress for
NSArray *achievementIDs = [NSArray arrayWithObjects:@"Achievement1", @"Achievement2", nil];

// Returns a dictionary with achievement ID's as keys and progresses as values
NSDictionary *achievementsProgress = [[GameCenterManager sharedManager] progressForAchievements:achievementIDs];  

To get the achievement progress for the current player for a single achievement:

// Returns a double value as achievement progress
double progress = [[GameCenterManager sharedManager] highScoreForLeaderboard:@"LeaderboardID"];  

###Reset Achievements Erase and reset all achievement progress from Game Center. Be warned though, the resetAchievements: method does not prompt the user before resetting - you must do this on your own. Currently, achievements are properly removed from Game Center, however a caching issue causes them to remain locally. Please submit a pull request if you can fix this issue.

[[GameCenterManager sharedManager] resetAchievementsWithCompletionHandler:^(NSError *error) {
    if (error) NSLog(@"Error: %@", error);
}];

When the resetAchievements: method is called and resets all achievements, the completion handler is fired. Use the completion handler for retrieving errors or updating user interface elements (ex. updating a table view listing completed achievements).

###Get Challenges Get challenges for the current game and player on iOS 6 and higher (GameCenterManager will check if challenges are supported on the current device). This method uses a completion handler to pass data (either an NSError or NSArray with the challenges. If the GKChallenge class or GameCenter is not available, the gameCenterManager: error: delegate method is called.

// Gets an array with challenges and passes the value to a completion handler.
[[GameCenterManager sharedManager] getChallengesWithCompletion:^(NSArray *challenges, NSError *error) {
    NSLog(@"Challenges: %@ \n Error: %@", challenges, error);
}];

If there is an error retrieving the challenges, the NSArray will be nil and the NSError will contain an error. The NSError passed here is an error generated by Game Center, not GameCenterMananger

##Player Data GameCenterManager provides four different methods to retrieve various bits of data about the current local player. Retrieve a player ID using the following method, but never display a player ID in your interface or expose the ID in any way at all - it should only be used to identify a player. If you display a player ID in your app, it will be rejected from the AppStore.

NSString *playerID = [[GameCenterManager sharedManager] localPlayerId];  

To get the player's display name (alias on iOS lower than iOS 6.0) use this method:

NSString *playerName = [[GameCenterManager sharedManager] localPlayerDisplayName];  

To get the player's profile picture the following method. On iOS, the completion handler passes a UIImage, on OS X the completion handler passes an NSImage. The image passed to you is at full resolution.

[self localPlayerPhoto:^(UIImage *playerPhoto) {
    UIImageView *imageView = [[UIImageView alloc] initWithImage:playerPhoto];
}];    

To get any other data about a player use this method:

GKLocalPlayer *player = [[GameCenterManager sharedManager] localPlayerData]; 

GameCenterManager delegate methods notify you of the status of Game Center and various other tasks. There is only one required delegate method for iOS, none for OS X.

Constants are used throughout GameCenterManager in error messages and method parameters.

###Score Sort Order The order in which your leaderboard scores are sorted. This helps GameCenterManager decide how to submit a score to a leaderboard (and determine if it is a highscore).
- GameCenterSortOrderHighToLow sorts scores from highest to lowest
- GameCenterSortOrderLowToHigh sorts scores from lowest to highest

###Error Codes When the gameCenterManager: error: delegate is called, one of the following error codes are passed.
- GCMErrorUnknown (0) an unknown error occured
- GCMErrorNotAvailable (1) the feature is not available or GameCenter is not available
- GCMErrorFeatureNotAvailable (2) the request feature is not available, check error message for info
- GCMErrorInternetNotAvailable (3) no internet connection - GCMErrorAchievementDataMissing (3) could not save achievement because the data was formatted improperly or is missing

See the Changelog.md file for details on updates. For the most updated information, take a look at the project releases.

See the License.md file for details on licensing this work / project, and attribution to other projects.