UILabel does not update each time with for loop

Question

I'm trying to animate my label in my UICollectionViewCell. I want to go randomly through the array and set the label randomly 10 times and then it stops at a random string from my array.

The problem is, it goes through my array (debugged it with a simple NSLog) BUT the label setText isn't used till the last number of my loop and the label is then set.

Here is my code:

-(void)animate{

    long index;

    for(detail* cells in [[self col] visibleCells]){

        NSIndexPath *indexPath = [[self col] indexPathForCell:cells];

        if ([array count] >= 3) {
            index = 2 * indexPath.section + indexPath.row;
        }else{
            index = 1 * indexPath.section + indexPath.row;
        }

        for (int i = 0; i <= 10; i++) {
            [[cells detailLabel] setText: [[array objectAtIndex:index] returnRandomOptie]];
            [NSThread sleepForTimeInterval:0.10];
            NSLog(@"%i", i);
        }

    }
}

And here is my returnRandomOptie from my custom Cell class:

-(NSString *) returnRandomOptie {
    NSUInteger randomIndex;
    NSString *string;

    if ([opties count] != 0) {
        randomIndex = arc4random() % [opties count];
        string = [NSString stringWithFormat:@"%@", [opties objectAtIndex:randomIndex]];
    }

    return string;
}

So basically I want that the for loop in my animate method, always sets the text in my label. And now it doesn't do that. Just at the last loop.

What am I doing wrong?

Kind Regards!

Answer 1

You have to perform the sleep async and update the label in the main thread, try this instead :

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    for (int i = 0; i <= 10; i++) {
        dispatch_async(dispatch_get_main_queue(), ^{
            [[cells detailLabel] setText: [[array objectAtIndex:index] returnRandomOptie]];
        });
        [NSThread sleepForTimeInterval:0.10];
        NSLog(@"%i", i);
    }
});    

Answer 2

Try this,

-(void)animate{
   ....
   for (int i = 0; i <= 10; i++) {
            dispatch_async(dispatch_get_main_queue(), ^{
                [[cells detailLabel] setText: [[array objectAtIndex:index] returnRandomOptie]];
            });

            [NSThread sleepForTimeInterval:0.10];
            NSLog(@"%i", i);
   }
   ...
}