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A Note on Swift Conversion

This branch of the project is currently being refactored and rewritten in Swift. Please contibute to help finish the conversion and improve the project. Once completed, the projct will switch over to Swift from Objective-C. Until that time, this branch is not ready for production use.

GameCenter Manager helps to manage Game Center in iOS and Mac apps. Report and track 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. On iOS (and soon on other platforms) GameCenter Manager makes it easy to setup and run live peer-to-peer Game Center Multiplayer matches.

If you like the project, please star it on GitHub! Watch the project on GitHub for updates. If you use GameCenter Manager in your app, send an email to or let us know on Twitter @iRareMedia.

Project Features

GameCenter Manager is a great way to use Game Center in your iOS or OS X app. Below are a few key project features and highlights.

  • Sync, submit, save, retrieve, and track any Game Center leaderboards, achievements, or challenges in only one line of code.
  • Setup and manage peer-to-peer multiplayer Game Center matches
  • Just drag and drop the files into your project - no complicated setup
  • Useful delegate methods and properties let you access and manage advanced Game Center features
  • iOS / OS X sample apps illustrate how easy it is to use GameCenter Manager

Project Information

Learn more about the project requirements, licensing, and contributions.


  • Built with and for Objective-C ARC
  • Requires a minimum of iOS 7.0 / OS X 10.9 as the deployment target
  • Requires Xcode 5.0.1 for use in any iOS Project
  • Uses Apple LLVM compiler 5.0


  • Requires iOS 7.0+ or OS X 10.9+. The sample project is optimized for iOS 8 and OS X 10.10.
  • Requires Automatic Reference Counting (ARC).
  • Optimized for ARM64 Architecture

Requires Xcode 6 for use in any iOS or OS X project. Requires a minimum of iOS 7.0 or OS X 10.9 as the deployment target.

Current Build Target Earliest Supported Build Target Earliest Compatible Build Target
iOS 9.0 iOS 7.0 iOS 7.0
OS X 10.11 OS X 10.9 OS X 10.9
Xcode 7.1 Xcode 6.1.1 Xcode 6.0
LLVM 6.1 LLVM 6.1 LLVM 5.0

Supported means that the library has been tested with this version. Compatible means that the library should work on this OS version (i.e. it doesn't rely on any unavailable SDK features) but is no longer being tested for compatibility and may require tweaking or bug fixes to run correctly.


You are free to make changes and use this in either personal or commercial projects. Attribution is not required, but is appreciated. We have spent a lot of time, energy, and resources working on this project - so a little Thanks! (or something to that affect) would be much appreciated. If you use GameCenter Manager in your app, send an email to or let us know on Twitter @iRareMedia. See the full GameCenter Manager license here.


Any contribution is more than welcome! You can contribute through pull requests and issues on GitHub.

Sample App

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 GameCenter Manager, documentation is available directly within Xcode (just Option-Click any method for Quick Help).


Setting up GameCenter Manager is very straightforward. These instructions do not detail how to enable Game Center in your app. You need to setup Game Center before using GameCenter Manager. Refer to the wiki pages for details on that.

  1. Add the GameKit, SystemConfiguration, and Security 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
    • Reachability
    • NSDataAES256
  3. Import the GameCenterManager.h file

  4. You can initialize GameCenterManager and begin syncing by using the following method call:

     [[GameCenterManager sharedManager] setupManager]; // Or use setupManagerAndSetShouldCryptWithKey: for use with encryption
  5. 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];


There are many methods available on iCloud Document Sync. The most important / highlight methods are documented below. All other methods are documented in the docset and with in-code comments.

Initialize GameCenterManager

You should setup GameCenterManager when your app is launched. This should only be done once and can be done in the application: didFinishLaunchingWithOptions: method of your AppDelegate.

[[GameCenterManager sharedManager] setupManager];

This initializes GameCenter Manager, checks if Game Center is supported on the current device, authenticates the player and synchronizes scores and achievements from Game Center. Alternatively, you can call the following method to enable encryption of local data:

[[GameCenterManager sharedManager] setupManagerAndSetShouldCryptWithKey:@"YourKey"];

These methods are not interchangable. If you decide to setup with encryption then you should never revert to setting up without encryption, and vice versa. Doing so will cause issues with archiving and unarchiving the saved data - which results in a crash. Pick one and stick with it forever. If you do change it, you'll need to delete the GameCenterManager.plist file from your app's library (inside the bundle).

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).

// Will not call delegate if status has not changed from the previous time it was called
BOOL isAvailable = [[GameCenterManager sharedManager] checkGameCenterAvailability:NO];

// Will always call delegate even if status has not changed from the previous time it was called
BOOL isAvailable = [[GameCenterManager sharedManager] checkGameCenterAvailability:YES];

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 (long long integer) as a high scores

long long 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

Presenting GameKit ViewControllers

GameCenter Manager makes the presentation of GameKit ViewControllers easy one-liners.

To present the leaderboards view controller, call the following method:

 // If you have one leaderboard, present the leaderboard
 // If you have more than one, shows all leaderboards and allows player to choose which one to show
 [[GameCenterManager sharedManager] presentLeaderboardsOnViewController:self withLeaderboard:nil];

 // Presents the leaderboard with the ID of LeaderboardID
 [[GameCenterManager sharedManager] presentLeaderboardsOnViewController:self withLeaderboard:@"LeaderboardID"];

To present the achievements view controller, call the following method:

 [[GameCenterManager sharedManager] presentAchievementsOnViewController:self];

To present the challenges view controller, call the following method:

 [[GameCenterManager sharedManager] presentChallengesOnViewController:self];

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) { // On OS X, the completion handler pases an NSImage instead of a UIImage
    UIImageView *imageView = [[UIImageView alloc] initWithImage:playerPhoto];

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

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


GameCenter Manager 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.

Authenticate User (Required, iOS only)

If the user is not logged into Game Center, you'll need to present the Game Center login view controller. This method is required because the user must be logged in for Game Center to work. If the user does not login, an error will be returned.

 - (void)gameCenterManager:(GameCenterManager *)manager authenticateUser:(UIViewController *)gameCenterLoginController

Availability Changed

When the availability status of Game Center changes, this delegate method is called. The availability of Game Center depends on multiple factors including: * Internet Connection * iOS Version (4.1+ required) * Player Authentication * Game Authentication

The NSDictionary object, availabilityInformation, contains two objects, a message and a title. The message object is an NSString describing the availability issue. The title is a shorter description of the error; it is also an NSString.

- (void)gameCenterManager:(GameCenterManager *)manager availabilityChanged:(NSDictionary *)availabilityInformation

Game Center Error

When there is an error performing a Game Center task this delegate method is executed.

The error NSError object contains an error code (refer to the section on Constants below), a description (error domain) and sometimes user information.

- (void)gameCenterManager:(GameCenterManager *)manager error:(NSError *)error

Reported Score

Called after the submitted score is successfully saved, uploaded, and posted to Game Center.

The GKScore object, score, is the final score that was saved. The error object may contain an error if one occured, or it may be nil.

- (void)gameCenterManager:(GameCenterManager *)manager reportedScore:(GKScore *)score withError:(NSError *)error;

Saved Score

Called after the submitted score is successfully saved, but not posted or uploaded to Game Center. The saved score will be uploaded the next time GC Manager can successfully connect to Game Center.

The GKScore object, score contains information about the submitted score.

- (void)gameCenterManager:(GameCenterManager *)manager didSaveScore:(GKScore *)score

Reported Achievement

Called after the submitted achievement and its percent complete is successfully saved, uploaded, and posted to Game Center.

The GKAchievement object, achievement, is the final achievement that was saved. The error object may contain an error if one occured, or it may be nil.

- (void)gameCenterManager:(GameCenterManager *)manager reportedAchievement:(GKAchievement *)achievement withError:(NSError *)error

Saved Achievement

Called after the submitted achievement is successfully saved, but not posted or uploaded to Game Center. The saved achievement and its percent completed will be uploaded the next time GC Manager can successfully connect to Game Center.

The GKAchievement object, achievement, is the final achievement that was saved.

- (void)gameCenterManager:(GameCenterManager *)manager didSaveAchievement:(GKAchievement *)achievement


Constants are used throughout GameCenter Manager 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