Question

Does GameKit allow you to invite a specific Game Center friend to a match, programmatically, i.e. without presenting the GC ViewController? The following handleInviteFromGameCenter documentation seems to imply that you can populate GKMatchRequest.playersToInvite and use it with [GKTurnBasedMatch findMatchForRequest]:

When your delegate receives this message, your application should create a new GKMatchRequest object and assign the playersToInvite parameter to the match request’s playersToInvite property. Then, your application can either call the GKTurnBasedMatch class method findMatchForRequest:withCompletionHandler: to find a match programmatically or it can use the request to instantiate a new GKTurnBasedMatchmakerViewController to show a user interface to the player.

But I’m finding that when findMatchForRequest calls my completion block with the populated match, the GameCenter ID I passed to it is not set as the 2nd player. Instead it’s empty and the status is “matching”. And therefore, when I call endTurnWithNextParticipant, it succeeds, but the invite isn’t received on my 2nd device. This illustrates what I’m doing:

GKMatchRequest *request = [[[GKMatchRequest alloc] init] autorelease]; 
request.minPlayers = 2;
request.maxPlayers = 2;
request.playersToInvite = [NSArray arrayWithObjects: otherPlayerGCID,nil ];

[GKTurnBasedMatch findMatchForRequest:request 
                  withCompletionHandler:^(GKTurnBasedMatch *match, NSError *error) 
{
    if (error) 
        NSLog(@"returned from fimdmatch but with error");
    else if (match != nil) {
        NSLog(@"match returned success and match populated");
        NSArray* otherPlayers = [match participants];
        if (otherPlayers.count>1) {
           NSData* placeholder = [@"no data" dataUsingEncoding:NSUTF8StringEncoding];
           [match endTurnWithNextParticipant:[otherPlayers objectAtIndex:1] 
                  matchData:placeholder 
                  completionHandler:^(NSError *error) 
           {
              if (error) 
                 NSLog(@"returned from END TURN but with error");
              else
                 NSLog(@"returned from  END TURN successfully");
           }];     

        }
     }
     else
        System::log("match returned success but match NOT populated");
}];

And like the person who seems to be having a similar problem here Game Center inviting friends progammatically, if I insert a call to the view controller, in my case GKTurnBasedMatchmakerViewController, all seems to work.

Thanks.

UPDATED:
I did see in an Apple Developer’s presentation on turn-based GC, a mention of something like, “If you want to invite a GC friend, we ask that you go through the GC view controller.

Any insight appreciated. Thanks again.

Answer 1

Wanted to share what I learned on this: As of iOS 5 there is not a way to invite a game center friend to play a game without going through the pre-defined GKTurnBasedMatchmakerViewController flow, which is optimized for starting a match in real time, guiding the user through three different screens.

After being urged to do so by apple dev support, I did submit a feature request to be able to invoke a simple, one-page view controller that would allow the user to send an invite / “recommend game” message via game center.

UPDATE FOR iOS 6:
Happy to report that it looks like this has been addressed in iOS 6. My original programmatic (non-UI) example above now works as originally expected.