iphone - 核心数据 : inserting Objects crashed in global queue [ARC - iPhone simulator 6. 1]

Question

我有一个非常简单的 Core Data 演示，其中只有一个按钮。

当我点击“运行”按钮时，应用程序在 for 循环中创建了 10,000 个对象，该对象在全局队列中运行。

更新更多细节:如果我将 for 循环放在主线程中，它运行良好。

更新我的意图:我知道 MOC 不是线程安全的，但根据 the Apple doc ，我们也可以使用串行队列访问MOC，串行队列使用多个线程。

这里我创建了核心数据栈:

#pragma mark - Core Data Stack

- (NSManagedObjectContext *)managedObjectContext
{
    if (nil != _managedObjectContext) {
        return _managedObjectContext;
    }

    _managedObjectContext = [[NSManagedObjectContext alloc] init];

    if (self.persistentStoreCoordinator) {
        [_managedObjectContext setPersistentStoreCoordinator:self.persistentStoreCoordinator];
    }

    return _managedObjectContext;
}

- (NSManagedObjectModel *)managedObjectModel
{
    if (nil != _managedObjectModel) {
        return _managedObjectModel;
    }

    _managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil];
    return _managedObjectModel;
}

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

    NSString *storeType = NSSQLiteStoreType;
    NSString *storeName = @"model.sqlite";
    NSURL *storeURL = [NSURL fileURLWithPath:[[self applicationDocumentsDirectory] stringByAppendingPathComponent:storeName]];

    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:self.managedObjectModel];

    NSError *error = nil;
    if (![_persistentStoreCoordinator addPersistentStoreWithType:storeType
                                                   configuration:nil
                                                             URL:storeURL
                                                         options:nil
                                                           error:&error])
    {
        NSLog(@"Error : %@\n", [error localizedDescription]);
        NSAssert1(YES, @"Failed to create store %@ with NSSQLiteStoreType", [storeURL path]);
    }

    return _persistentStoreCoordinator;
}

#pragma mark -
#pragma mark Application's Documents Directory

- (NSString *)applicationDocumentsDirectory
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
    return basePath;
}

应用启动后:

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    // Override point for customization after application launch.

    if (self.managedObjectContext) {
        ;
    }

    return YES;
}

当我点击按钮时:

- (IBAction)runButtonDidClick:(id)sender
{
    /**
     * Access the moc using different threads to make deadlock.
     */

    [self runSave];
}

- (void)runSave
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
        NSManagedObjectContext *moc = appDelegate.managedObjectContext;

        if (moc) {
            for (int j = 0; j < 10000; ++j) {
                People *people = [NSEntityDescription insertNewObjectForEntityForName:@"People" inManagedObjectContext:moc];
                people.name = @"noname";
            }

            NSLog(@"**********IN SAVE %@", [NSThread currentThread]);
            NSError *error = nil;
            if ([moc save:&error]) {
                ;
            }

            NSLog(@"**********OUT SAVE %@", [NSThread currentThread]);
        }
    });
}

点击运行按钮几次，可能是 2 次或 3 次或 4 次……它崩溃了

我想不通为什么...感谢您的帮助。

Answer 1

核心数据应该始终在有 moc 的线程上工作。performBlock 和performBlockAndWait 的唯一工作是负责线程安全。通过它插入核心数据将始终在正确的线程中运行。您可以在任何线程上定义 moc - performBlock 始终选择正确的线程。

所以:

[self.managedObjectContext performBlock:^{
            for(NSDictionary *dic in arr) {
                //inserting here!
            }
}];

在你的情况下:

- (void)runSave
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
        NSManagedObjectContext *moc = appDelegate.managedObjectContext;

        if (moc) {

          [moc performBlock:^{
            for (int j = 0; j < 10000; ++j) {
                People *people = [NSEntityDescription insertNewObjectForEntityForName:@"People" inManagedObjectContext:moc];
                people.name = @"noname";
            }
            NSError *error = nil;
            if ([moc save:&error]) {
                ;
            }
         }];
        }
    });
}