使用persistentStoreCoordinator随机EXC_BAD_ACCESS

Question

我的应用程序有时会在完全加载到以下行之前崩溃:

if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error])

这个if状态所在的完整方法如下(我认为这是非常标准的):

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (__persistentStoreCoordinator != nil) {
        return __persistentStoreCoordinator;
    }

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"CoreData.sqlite"];

    NSError *error = nil;
    __persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }    

    return __persistentStoreCoordinator;
}

更新

第二次-(NSPersistentStoreCoordinator *)persistentStoreCoordinator调用该方法时发生崩溃.编辑 从第一个可见的viewController调用它的第一次:

- (void)updateStats {
    NSLog(@"Updating stats");
    dispatch_queue_t request_queue = dispatch_queue_create("updateNumberOfSchedules", NULL);
    dispatch_async(request_queue, ^{
         AppDelegate *theDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init];
    [context setPersistentStoreCoordinator:[theDelegate persistentStoreCoordinator]];
    ...
    });
}

第二次(当我的DeviceLinker类要在checkInactiveLinks方法中检查数据库中的非活动链接时,有时会发生崩溃.此方法在启动时调用applicationDidBecomeActive:

-(void) checkInactiveLinks {
    AppDelegate *theDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
    NSManagedObjectContext *newMoc = [[NSManagedObjectContext alloc] init];
    [newMoc setPersistentStoreCoordinator:[theDelegate persistentStoreCoordinator]];
    ...
}

纠正我如果我错了但是读了我的代码我会认为第二次调用persistentStoreCoordinator getter它应该返回__persistentStoreCoordinator并且不分配并初始化一个新的...

更新2 在if语句的同一行上我也经常得到这个:

-[__NSCFDictionary _hasPrecomputedKeyOrder]: unrecognized selector sent to instance 0x7dd3770

更新3

我编辑了我的构建方案,并在诊断选项卡下打开了僵尸和日志异常.现在我明白了-[NSPersistentStoreCoordinator unlock]: message sent to deallocated instance 0x8916090.请注意,我的代码中没有任何显式锁.

Answer 1

看起来您正在同时从多个线程进入该段代码.当你进行延迟实例化时,你必须确保只通过一个执行线程的"第一次"将同时通过.您可以使用以下策略在主线程上同步对它的访问.

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (__persistentStoreCoordinator != nil) {
        return __persistentStoreCoordinator;
    }

    // Add this block of code.  Basically, it forces all threads that reach this
    // code to be processed in an ordered manner on the main thread.  The first
    // one will initialize the data, and the rest will just return with that
    // data.  However, it ensures the creation is not attempted multiple times.
    if (![NSThread currentThread].isMainThread) {
        dispatch_sync(dispatch_get_main_queue(), ^{
            (void)[self persistentStoreCoordinator];
        });
        return __persistentStoreCoordinator;
    }

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"CoreData.sqlite"];

    NSError *error = nil;
    __persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }    

    return __persistentStoreCoordinator;
}