ios – 核心数据并发调试：假阳性

如 WWDC 2014 session 225(核心数据新增内容)所述,iOS 8和OS X优胜美地的核心数据现在支持命令行参数-com.apple.CoreData.ConcurrencyDebug 1,以启用检测到违反Core Data的并发合同的断言.

在我的实验中,我发现它在iOS 8 beta 1(在设备和模拟器中)都可以工作,但是我似乎发现了一个错误的肯定,即框架是抛出一个多线程违规异常不这样做至少这是我的信仰.

问题：下面的代码是正确的还是我做的事情违反了Core Data的线程模型？

我所做的是设置一个非常简单的核心数据堆栈(使用内存存储,为了简单起见)与托管对象上下文名为backgroundContext与私有队列并发.然后我在该上下文中调用performBlockAndWait {},并在块中创建一个新的托管对象,将其插入上下文并保存.

保存操作是从Core Data获取多线程冲突异常的地方.

var backgroundContext: NSManagedobjectContext?

func setupCoreDataStackAndViolateThreadingContract()
{
    let objectModelURL = NSBundle.mainBundle().URLForResource("CoreDataDebugging",withExtension: "momd")
    let objectModel: NSManagedobjectModel? = NSManagedobjectModel(contentsOfURL: objectModelURL)
    assert(objectModel)

    // Set up a simple in-memory Store (without error handling)
    let storeCoordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedobjectModel: objectModel)
    assert(storeCoordinator)
    let store: NSPersistentStore? = storeCoordinator!.addPersistentStoreWithType(NSInMemoryStoreType,configuration: nil,URL: nil,options: nil,error: nil)
    assert(store)

    // Set up a managed object context with private queue concurrency
    backgroundContext = NSManagedobjectContext(concurrencyType: .PrivateQueueConcurrencyType)
    assert(backgroundContext)
    backgroundContext!.persistentStoreCoordinator = storeCoordinator!

    // Work on the background context by using performBlock:
    // This should work but throws a multithreading violation exception on 
    // self.backgroundContext!.save(&potentialSaveError)
    backgroundContext!.performBlockAndWait {
        NSEntityDescription.insertNewObjectForEntityForName("Person",inManagedobjectContext: self.backgroundContext!) as NSManagedobject
        person.setValue("John Appleseed",forKey: "name")

        var potentialSaveError: NSError?
        // In the following line: EXC_BAD_INSTRUCTION in
        // `+[NSManagedobjectContext __Multithreading_Violation_AllThatIsLeftToUsIsHonor__]:
        let didSave = self.backgroundContext!.save(&potentialSaveError)
        if (didSave) {
            println("Saving successful")
        } else {
            let saveError = potentialSaveError!
            println("Saving Failed with error: \(saveError)")
        }
    }
}

我已经在Objective-C中基本上测试了相同的代码,并得到相同的结果,所以我怀疑这是一个Swift的问题.

编辑：如果你想自己运行代码,那么I have put a project on GitHub(需要Xcode 6 / iOS 8 beta).