Game Center integration

Matchmaker, matchmaker find me a match! Now's the time to start finding our friends!

Let's pop over to our MultiplayerHelper.h file so that we can add in a new dictionary to store the players we find. Just after the @interface line, add in the following declaration:

@property(nonatomic, strong) NSMutableDictionary *playersDict;

This dictionary allows Game Kit to easily look up player data.

Now, we will go over to our MultiplayerHelper.m file and make a few new changes. First, we will add a new method just after we authenticate our local player:

- (void)lookupPlayers {
    
    NSLog(@"Looking up %lu players...", (unsigned long)_match.playerIDs.count);
    
    [GKPlayer loadPlayersForIdentifiers:_match.playerIDs withCompletionHandler:^(NSArray *players, NSError *error) {
        
        if (error != nil) {
            NSLog(@"Error retrieving player info: %@", error.localizedDescription);
            _matchStarted = NO;
            [_delegate matchEnded];
        } else...