Question

imagine there is no internet connection when user is playing. The score cannot be submitted to game center. However I save the highscore on the phone using NSUserDefaults too.

So when the user plays next time and is connected to game center should I sync this score he achieved playing “offline”?

Is that a good practice?

Answer 1

Per the Apple Game Center docs, the answer is YES.

Make Sure Your Game Sends Data Again After a Network Failure

When you implement leaderboards or achievements, your game reports a
player’s scores or achievement progress to Game Center. However,
networking is never perfectly reliable. If a networking error occurs,
your game should save the Game Kit object and retry the action again
at a later time. Both the GKScore and GKAchievement classes support
the NSCoding protocol, so your game can archive those objects when it
moves into the background.

Set up a cache that keeps your score data (I use NSUserDefaults) to preserve data between sessions, and every so often (like, each time the user enters the app) test to see if Game Center is reachable, and if so, upload your cached scores. Let me know if you need any code – this post is pretty old, so I won’t be surprised if no one ever answers 🙂