People love to play games. Games on the App Store are no exception—games continue to be the most popular category of apps on iOS. Games are inherently a social activity. Sometimes, this social interaction is part of the game itself, such as when the game provides competitive or cooperative multiplayer gameplay. But even for games intended for single-player experiences, players like to see and share their accomplishments.
Because social gaming is such an important part of the game-playing experience, Apple supports it directly with the Game Center service. Game Center allows a player’s devices to connect to the Game Center service and exchange information.
Each player performs different activities but all of them are interacting with Game Center:
Bob uses the Game Center app provided by Apple to view his scores earned in a game that supports Game Center. The Game Center app shows both Bob’s scores and scores earned by other players. Even though the scores are displayed by the Game Center app, the score data and formatting are provided to Game Center by the game.
Joe is playing an adventure game that supports achievements. He just discovered an item for a quest he wants to complete. The game sends a message to Game Center to update the progress stored there.
Mary, Alice, and Charlie are playing a game that supports Game Center’s matchmaking. Game Center allows the three players devices to find and connect to each other. The game exchanges data between the participants through Game Center’s servers.
Sara plays another multiplayer game also using Game Center’s matchmaking. Sara’s game supports turn-based play and Sara has received a push notification that it is her turn to act.
Game Center is best viewed as a collection of interconnected components that provide features both to game developers and to end-users:
The Game Center service is the online portion of Game Center. The Game Center servers store player and game data and vend the data and other services to OS X and iOS devices.
The Game Kit framework provides classes that developers use to add support for Game Center to their games. Game Kit is available starting in iOS 4.1 and OS X v10.8.
The Game Center app provides a centralized app that players use to access Game Center’s features.
For players to take advantage of Game Center in your game—and for your game to be visible in the Game Center app—you must explicitly add support for Game Center to your game. You do this by implementing authentication and then at least one other Game Center feature.