Integrate Game Center features using GameKit. Use when authenticating GKLocalPlayer, checking player restrictions, submitting leaderboard scores, reporting achievements, implementing real-time or turn-based matchmaking, handling GKMatch data, showing the Game Center dashboard or access point, adding

GameKit Use GameKit for Game Center authentication, competition, matchmaking, social surfaces, and saved game handoffs; keep rendering, board logic, and full SharePlay group activity design in their owning framework skills. Contents [Authentication]( authentication) [Access Point]( access point) [Dashboard]( dashboard) [Leaderboards]( leaderboards) [Achievements]( achievements) [Real Time Multiplayer]( real time multiplayer) [Turn Based Multiplayer]( turn based multiplayer) [Common Mistakes]( common mistakes) [Review Checklist]( review checklist) [References]( references) Authentication All GameKit features require the local player to authenticate first. Set the authenticateHandler on GKLocalPlayer.local early in the app lifecycle. GameKit calls the handler multiple times during initialization. Guard on GKLocalPlayer.local.isAuthenticated before calling any GameKit API. For server side identity verification, see [references/gamekit patterns.md](references/gamekit patterns.md). Access Point GKAccessPoint displays a Game Center control in a corner of the screen. When tapped, it opens the Game Center dashboard. Configure it after authentication. Hide the access point during gameplay and show it on menu screens: Open the dashboard to a specific state programmatically. Specific leaderboard access point triggers require iOS 18+. Dashboard Present the Game Center dashboard using GKGameCenterViewController . The presenting object must conform to GKGameCenterControllerDelegate . Dashboard states include .dashboard , .leaderboards , .achievements , .challenges , .localPlayerProfile , and .localPlayerFriendsList . Leaderboards Configure leaderboards in App Store Connect before submitting scores. Supports classic (persistent) and recurring (time limited, auto resetting) types. Submitting Scores Submit to one or more leaderboards using the class method: Loading Entries GKLeaderboard.Entry provides player , rank , score , formattedScore , context , and date . For recurring leaderboard timing, leaderboard images, and leaderboard sets, see [references/gamekit patterns.md](references/gamekit patterns.md). Achievements Configure achievements in App Store Connect. Each achievement has a unique identifier, point value, and localized title/description. Reporting Progress Set percentComplete from 0...100 . The property type is Double , but Apple requires an integer value. GameKit only accepts increases. Loading Player Achievements If an achievement is not returned, the player has no progress on it yet. Create a new GKAchievement(identifier:) to begin reporting. Use GKAchievement.resetAchievements() to reset all progress during testing. Real Time Multiplayer Real time multiplayer connects players in a peer to peer network for simultaneous gameplay. Players exchange data directly through GKMatch . Matchmaking with GameKit UI Use GKMatchmakerViewController for the standard matchmaking interface: Implement GKMatchmakerViewControllerDelegate : Exchanging Data Send and receive game state through GKMatch and GKMatchDelegate : Data modes: .reliable sends until delivery succeeds or the connection times out; .unreliable sends once and may arrive out of order. Use .reliable for critical state and .unreliable for small, time sensitive updates. Treat received match data as untrusted input. Register the local player as a listener ( GKLocalPlayer.local.register(self) ) to receive invitations. For programmatic matchmaking and custom match UI, see [references/gamekit patterns.md](references/gamekit patterns.md). Turn Based Multiplayer Turn based games store match state on Game Center servers. Players take turns asynchronously and do not need to be online simultaneously. Starting a Match Taking Turns Encode game state into Data , end the turn, and specify the next participants: Ending the Match Set outcomes for all participants, then end the match: Listening for Turn Events Register as a listener. Prefer GKLocalPlayerListener when one object handles multiple Game Center event categories. Match Data Size Check the match object's matchDataMaximumSize before ending a turn. Store larger state externally and keep only compact references in match data. Common Mistakes Not authenticating before using GameKit APIs Setting authenticateHandler multiple times Ignoring multiplayer restrictions Not setting match delegate immediately Not calling finishMatchmaking for programmatic matches Not disconnecting from match Review Checklist [ ] GKLocalPlayer.local.authenticateHandler set once at app launch [ ] isAuthenticated checked before any GameKit API call [ ] Player restrictions checked ( isUnderage , isMultiplayerGamingRestricted , isPersonalizedCommunicationRestricted ) [ ] Game Center capability added in Xcode signing settings [ ] Leaderboards and achievements configured in App Store Connect [ ] Access point configured and toggled appropriately during gameplay [ ] GKGameCenterControllerDelegate dismisses dashboard in gameCenterViewControllerDidFinish [ ] Match delegate set immediately when match is found [ ] finishMatchmaking(for:) called for programmatic matches; disconnect() and nil delegate on exit [ ] Turn based match data stays under match.matchDataMaximumSize [ ] Turn based participants have outcomes set before endMatchInTurn [ ] Invitation or turn listener registered with GKLocalPlayer.local.register( :) [ ] Data mode chosen appropriately: .reliable for state, .unreliable for frequent updates [ ] Error handling for all async GameKit calls References See [references/gamekit patterns.md](references/gamekit patterns.md) for identity verification, legacy voice chat, saved games, custom match UI, leaderboard images, challenge handling, and rule based matchmaking. [GameKit documentation](https://sosumi.ai/documentation/gamekit) [GKLocalPlayer](https://sosumi.ai/documentation/gamekit/gklocalplayer) [GKAccessPoint](https://sosumi.ai/documentation/gamekit/gkaccesspoint) [GKLeaderboard](https://sosumi.ai/documentation/gamekit/gkleaderboard) [GKAchievement](https://sosumi.ai/documentation/gamekit/gkachievement) [GKMatch](https://sosumi.ai/documentation/gamekit/gkmatch) [GKTurnBasedMatch](https://sosumi.ai/documentation/gamekit/gkturnbasedmatch)