I am building a game which uses achievements currently.
Let's imagine the following situation:
The user starts the app the first time, does not sign in to GameCenter and gets a few achievements. But now he decides to use GameCenter and signs in some time later.
What happens to the gained achievements? Will they be sent to the GameCenter servers later on or do I need to program a check-for-gained-achievements method manually? What did you do?
Thanks for your help!
I stored the data locally in a plist and submit when they login.
In iOS 5 or newer iOS, you have another option to submit offline the achievements and scores when users are not logon to Game Center. This utility behaves as a local cache when users are offline, and it will submit the achievements and scores to Game Center next time the gamers logon to Game Center.
Here is the link a similar question to yours and the answer:
Offline Game Center iOS Achievements
Cheers.
Related
If I'd want to implement multiplayer checkers game using game center API, does it mean that I don't have to write a server, and I'll be using game center's servers?
I'm new to game center, and I'd like to know its use.
Thanks.
Here is a great tutorial that will get you up and running in a couple of hours!
Beginning Turn Based Gaming with iOS5
Yes, Obsolutely you don't want to write any servers. The apple's Game Center handles it. First of all you need to import GameKit framework. It will maintain game center servers.In Game Center you have Leaderboards (Where you can see the scores of all players who are using your app), and Achievements (You can setup some achievements that when a user crosses particular scores 1000, 2000, 3000.. etc. in your app). The Leaderboards and achievements are two different viewControllers you can show them through coding. For More Details You can visit the following link http://developer.apple.com/library/ios/#DOCUMENTATION/NetworkingInternet/Conceptual/GameKit_Guide/GameCenterOverview/GameCenterOverview.html it is very clear. And if you have any doubts feel free to contact me. I have implemented Leaderboards and achievements recently, but not multiplayer features. And to perform all these you have to enable GameCenter in your iTunes account.
As matter of fact in order to have a good multiplayer game experience, you need to consider eventually writing server side code that saves the user data in your database.
I have experienced the same scenario and ended it up using Parse along with push notifications.
If you insist you can do the following with Game Center :
With Game Center services you can connect players to each others either by Real-Time Matches or Turn-Based Matches. Everything is fine as long as you don't care about the user data storage or the game experience!
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?
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 :)
Also per the Apple docs for iOS 5.0 and later network error related issues are handled by a background reporting task so the developer does not need to write anything to handle this if not supporting previous iOS versions.
(from GKScore Class Reference for method reportScoreWithCompletionHandler:)
If the error is a network error and your game is running on iOS 4.3 or earlier, your game should periodically attempt to report the progress until the score is successfully reported. On iOS 5.0 and later, the background reporting task automatically handles network errors on your game’s behalf.
I am not sure what is supposed to happen if no one is logged into Game Center at all though (no network related/ submission issues) when a high score is achieved and then someone logs in later. In that case no GKScore object can even be created because there is no authenticated player and so there is no way to know who actually achieved the score whenever the next person logs into Game Center. Seems handling logged in (even without a network connection temporarily) is best practice but if no one is logged in at all and a high score is gained then it's just tough luck because it is not known who earned it, other than saving it as a device high score. If anyone handles that case then please tell.
Good question.
In my point of view, if a user is offline and is still playing, the score he/she scores should be saved locally. And when he/she again appears online, the offline score shouldn't be submitted online. Because if offline score is submitted, the purpose of making the game online is defeated.
I have successfully put game center leaderboards into my app with them updating the highscores correctly so I'm not worried about that.
The problem I am having is even though they are displaying and updating correctly in my app, when I view the leaderboards in the game center app it says there are no scores???
Anyone else has this trouble???
Disco
It seems there is just a delay between the gamecenter servers and the saving of highscores when developing.
While you develop your app all scores get submitted to the sandbox gamecenter servers.
Maybe you are logged in the live servers with the game center app ?
I am facing some problems, that is, In my application the gamecenter works fine , but when ever I run another application then the multiple player list not showing... when I click on the all month data (ie,. who is playing that game) it will give me only my info. not giving me the full detail
From Apple's Game Kit Programming Guide:
To help you test your application, Apple provides a sandbox environment for Game Center. This sandbox environment duplicates the live functionality of Game Center, but is separate from the live servers. The sandbox allows you to test your Game Center features without making your application visible to regular users.
When you log in to Game Center on the app you're developing, you're logged in to the sandboxed version of Game Center (for apps in development). To log back in to the standard Game Center environment, log yourself out and log back in from a different (i.e. released as opposed to in-development) game.
If I have an app that supports Game Center and I'd like to provide Achievements for completing a puzzle pack that's sold as an in-app purchase, how do I sync the iTunes account that's being charged for the in-app purchase with the Game Center user account that's doing the buying? As I understand it, they're two separate user accounts that are accessed in two different locations (The Game Center account is accessed in the Game Center app and the iTunes account is accessed in the Settings app).
How do I avoid this from happening...
Game Center Player1 logs in, runs my app and purchases a puzzle pack
Game Center Player1 logs out, Game Center Player2 logs in, runs my app and plays to completion the puzzle pack that Player1 purchased and Player2 is awarded the Achievement.
Game Center Player2 logs out, Game Center Player1 logs in and finds the puzzle pack he/she purchased as already completed, so Player1 is unable to gain that same achievement.
Am I misunderstanding something with how these user accounts work? If not, is there a way to sync a Game Center account with an iTunes account as players log in and out of my game? Is there any kind of a work around for this problem? This seems like it would be a fairly common issue with any multiplayer games that sell content.
Thanks so much!
That is a good question. :) As far as achievements go, I guess you could store them on the device with the playerId from the logged in GKPlayer, and once an achievement has been finished for a logged in player, you synch with Game Center.
As far as synching iTunes and Game Center accounts I really don't know. Usually you store some information on whether a purchase has been made (i.e. a feature available) on the device. Would it be logical that using that feature (or being allowed to use it) should be device dependent, not GC user dependent? But then what happens if someone uses their account to just download your content again and again to their friends' devices?
Hmm... I hope some other people will share their thoughts on this. But I found that Game Center questions receive very low views and answers :(
So here's how I'm going to do this, it's actually a fairly straightforward approach. I'm going to locally track users progress in the purchased puzzle packs using core data, since it's quick to get up and running. Each time a new GC user logs in, I'll create a new user object and track their progress in the puzzle packs and report the achievements in GC when needed. When that GC user logs in later, I'll just adjust the state of the puzzle packs to match their current progress defined in core data. This way, any iTunes account can purchase the puzzle packs and they'll inherently be available to anyone using the device. Whenever any GC users log into GC and play my app, they'll all have access to the same purchased puzzle packs, but their progress and achievements will be maintained independently of other GC users.
If GC isn't installed on the device, I can disable all GC features and just init the app as tho there's only one default player.
Should be simple to do.
I am trying to come up with the solution to resolve this issue as well. If using the server product delivery mode, the problem could be largely resolved. The application sends the purchased items to server;sever deliver the item to application after checking credentials. There are some corner cases I still don't know how to resolve, basically to handle the case when the whole flow is interrupted, which depeneds on the implementation of IAP. Still not 100% sure yet.
Could you keep a record on the phone about which achievements have been bought by particular users, and then check which user is on and either enable or disable the purchased content - you'd have to have a means of keeping track of different players progress (I can see potential problems where a user might not be logged in to GC, etc etc). I haven't done this yet, tho I'm planning it for my next game.