Is it possible to tag blocks?

Question

I am working on a turn based iOS game and trying to populate my list of games the player is participating in.

for (unsigned i = 0; i < [matches count]; i++)
{
    // Only load data for games in progress.
    // NOTE: Might want to handle finished games later.
    if ([matches[i] status] != GKTurnBasedMatchStatusEnded)
    {

        // Send off another block to retrieve the match's data.
        [(GKTurnBasedMatch*)matches[i] loadMatchDataWithCompletionHandler: ^(NSData *matchData, NSError *error)
         {
             // Prepare the game.
             Game* game;
             if (matchData.length == 0)
             {
                 // If the match data is empty, this is a new game. Init from scratch.
                 game = [[Game alloc] init];
             }
             else
             {
                 // Otherwise, unpack the data and init from it.
                 game = [NSKeyedUnarchiver unarchiveObjectWithData:matchData];
             }
             game.match = matches[i];

             // Load the displayNames for the players.
             bool lastIndex = i == ([matches count] - 1);
             [self loadPlayerIdentifiersForGame:game intoArray:blockGames lastIndex:lastIndex];
         }];
    }
}

Unfortunately, I am having an issue where I can't tag each block with its index. That is, i is always 0 by the time the block executes. Is there a way that I can make sure the block knows what i WAS at the time it was launched?

Answer 1

I sidestepped the issue where my UITableView wouldn't reload if the last game was over by doing this instead:

GKTurnBasedMatch* match;
for (int j = ([matches count] - 1); j >= 0; j --)
{
    match = matches[j];
    if (match.status != GKTurnBasedMatchStatusEnded)
        break;
}
bool lastIndex = (matches[i] == match);
[self loadPlayerIdentifiersForGame:game intoArray:blockGames lastIndex:lastIndex];

Answer 2

-(void)someMethod {
    ...
    for (unsigned i = 0; i < [matches count]; i++)
    {
        // Only load data for games in progress.
        // NOTE: Might want to handle finished games later.
        if ([matches[i] status] != GKTurnBasedMatchStatusEnded)
            [self loadMatch:i of:matches];
    }
}

-(void) loadMatch:(int)i of:(NSArray *)matches {
    // Send off another block to retrieve the match's data.
    [(GKTurnBasedMatch*)matches[i] loadMatchDataWithCompletionHandler: ^(NSData *matchData, NSError *error)
     {
         // Prepare the game.
         Game* game;
         if (matchData.length == 0)
         {
             // If the match data is empty, this is a new game. Init from scratch.
             game = [[Game alloc] init];
         }
         else
         {
             // Otherwise, unpack the data and init from it.
             game = [NSKeyedUnarchiver unarchiveObjectWithData:matchData];
         }
         game.match = matches[i];

         // Load the displayNames for the players.
         bool lastIndex = i == ([matches count] - 1);
         [self loadPlayerIdentifiersForGame:game intoArray:blockGames lastIndex:lastIndex];
     }];
}

Answer 3

the simplest way is to pass a third parameter containing the tag..

And I suggest to use typedef.. to better write code (and let autocompletion work for you..)

typedef void (^CompletionBlock)(NSInteger tag, NSData * data, NSError *err);

and use CompletionBlock when defining loadMatchDataWithCompletionHandler.