Question

Could someone please help me spot the leak. I don’t really know where my leak is. So I will post my code here and hopefully someone can spot it for me. In the leaks instrument it says responsible frame is dispatch_semaphore_create which I’m not calling?

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];

        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

        dispatch_group_t group = dispatch_group_create();

        dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

            if ([defaults boolForKey:@"notFirstRunSeminars"]) {

                BOOL isUpdated = self.seminarsParser.seminarsAreUpdated;

                if (isUpdated) {
                    DLog(@"Seminars have been updated");

                    [[NSNotificationCenter defaultCenter] 
                     postNotificationName:@"updateSeminarsTable" 
                     object:nil];

                    [[[[[self tabBarController] tabBar] items] objectAtIndex:kSeminarsTabIndex] setBadgeValue:self.seminarsParser.numberOfNewSeminars];
                    self.seminarsParser.numberOfNewSeminars = nil;

                }
            }
        });

        dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

            if ([defaults boolForKey:@"notFirstRunCareers"]) {

                BOOL isUpdated = self.careersParser.careersAreUpdated;

                if (isUpdated) {
                    DLog(@"Careers have been updated");

                    [[NSNotificationCenter defaultCenter] 
                     postNotificationName:@"updateCareersTable" 
                     object:nil];

                    [[[[[self tabBarController] tabBar] items] objectAtIndex:kCareersTabIndex] setBadgeValue:self.careersParser.numberOfNewCareers];
                    self.careersParser.numberOfNewCareers = nil;

                }
            }
        });

        dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

            if ([defaults boolForKey:@"notFirstRunOffices"]) {

                BOOL isUpdated = [officesParser officesAreUpdated];

                if (isUpdated) {
                    DLog(@"Offices have been updated");

                    [[NSNotificationCenter defaultCenter] 
                     postNotificationName:@"updateOfficesTable" 
                     object:nil];
                }
            }
        });

        dispatch_group_notify(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

            [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];

        });

    });

Answer 1

Where are you releasing the group after you’re done with it, since you’re creating a group within the outermost async block? That’s the only object I can see you creating which isn’t being released properly. Incidently, a group creates a semaphore behind the scenes (all a dispatch group really is, is some syntactic sugar around an internal dispatch semaphore), which is why instruments is reporting it that way.