Resolving Core Data Store Issues with Weak References and Synchronization in Objective-C Development

The infamous “55% of the time” mystery.

After carefully reviewing your code, I have identified several potential issues that could be contributing to this issue:

Leaks: You have multiple retain calls in a row without corresponding release calls. This can lead to memory leaks and unexpected behavior.
Retained objects: Your arrayOfRestrictedLotTitles, arrayOfALotTitles, etc., are being retained in the main thread, which could cause issues when accessed from another thread (e.g., the background thread accessing the Core Data Store).
Async access to Core Data: By using a background thread to access the Core Data Store, you’re introducing potential synchronization issues. Make sure that all shared data is properly synchronized between threads.
Nil values: If one of the NSDictionary or NSSet objects is nil, it could cause issues when trying to create the overlays.

To fix this issue, I recommend the following:

Remove all retain calls and use ARC (Automatic Reference Counting) instead, if possible.
Use weak references or pointers to avoid retain cycles.
Ensure proper synchronization between threads when accessing shared data (e.g., using a lock or a thread-safe data structure).
Verify that the Core Data Store is properly configured and that all data is being retrieved correctly.

To further help you, I have rewritten your loadOverlaysFromStore method to demonstrate how to use weak references, avoid retain cycles, and ensure proper synchronization:

-(void)loadOverlaysFromStore {
    NSLog(@"DataLoader.m loadOverlaysFromStore");
    
    // Use a lock to ensure thread safety
    @synchronized(self) {
        NSMutableArray *arrayOfRestrictedLotTitles = [[NSMutableArray alloc] init];
        NSMutableArray *arrayOfALotTitles = [[NSMutableArray alloc] init];
        NSMutableArray *arrayOfCLotTitles = [[NSMutableArray alloc] init];
        NSMutableArray *arrayOfLLotTitles = [[NSMutableArray alloc] init];

        NSDictionary *permits1 = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"0",@"0",@"0",nil] forKeys:[NSArray arrayWithObjects:@"A",@"C",@"L",nil]];
        NSSet *setOfRestrictedLots = [[NSSet setWithArray:[[CoreDataSingleton sharedManager] getParkingLotsForPermits:permits1]] copy];
        [arrayOfRestrictedLotTitles addObject:[(NSString *)setOfRestrictedLots firstObject]];

        NSDictionary *permits2 = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"1",@"0",@"0",nil] forKeys:[NSArray arrayWithObjects:@"A",@"C",@"L",nil]];
        NSSet *setOfALots = [[NSSet setWithArray:[[CoreDataSingleton sharedManager] getParkingLotsForPermits:permits2]] copy];
        [arrayOfALotTitles addObject:[(NSString *)setOfALots firstObject]];

        NSDictionary *permits3 = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"1",@"1",@"0",nil] forKeys:[NSArray arrayWithObjects:@"A",@"C",@"L",nil]];
        NSSet *setOfCLots = [[NSSet setWithArray:[[CoreDataSingleton sharedManager] getParkingLotsForPermits:permits3]] copy];
        [arrayOfCLotTitles addObject:[(NSString *)setOfCLots firstObject]];

        NSDictionary *permits4 = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"1",@"1",@"1",nil] forKeys:[NSArray arrayWithObjects:@"A",@"C",@"L",nil]];
        NSSet *setOfLLots = [[NSSet setWithArray:[[CoreDataSingleton sharedManager] getParkingLotsForPermits:permits4]] copy];
        [arrayOfLLotTitles addObject:[(NSString *)setOfLLots firstObject]];

        // Use weak references to avoid retain cycles
        __weak ParkingRegionOverlay *regionPolygon;
        for (NSSet* set in addedOverlays) {
            for (ParkingLot *lot in [set allObjects]) {
                regionPolygon = [[ParkingRegionOverlay alloc] initWithPoints:[lot overlayCoordPoints]
                                                                    andTitle:[lot lotName] 
                                                                       setRestricted:[NSSet setWithArray:arrayOfRestrictedLotTitles]
                                                                setA:[NSSet setWithArray:arrayOfALotTitles]
                                                                setC:[NSSet setWithArray:arrayOfCLotTitles]
                                                                setL:[NSSet setWithArray:arrayOfLLotTitles]];
                [overlayRegions addObject:regionPolygon];
                regionPolygon = nil;
            }
        }
    }
}

By using weak references, avoiding retain cycles, and ensuring proper synchronization, you should be able to fix the issue.

Last modified on 2025-01-16