如果启用方案“-com.apple.CoreData.ConcurrencyDebug 1”，为什么 raywenderlich 代码会中断

Question

此示例展示了如何使用 coreData 异步提取数据。如果你的运行程序没有方案 "-com.apple.CoreData.ConcurrencyDebug 1" 所有工作，但如果你打开方案 "-com.apple.CoreData.ConcurrencyDebug 1" 我们会得到运行时间错误. 为什么会这样我不知道

（我没有违反这些条款）来自苹果文档

Core Data is designed to work in a multithreaded environment. However, not every object under the Core Data framework is thread safe. To use Core Data in a multithreaded environment, ensure that:

Managed object contexts are bound to the thread (queue) that they are associated with upon initialization.

Managed objects retrieved from a context are bound to the same queue that the context is bound to.


Stack Trace

CoreData`+[NSManagedObjectContext __Multithreading_Violation_AllThatIsLeftToUsIsHonor__]:
    0x7fff23a8a65e <+0>: pushq  %rbp
    0x7fff23a8a65f <+1>: movq   %rsp, %rbp
->  0x7fff23a8a662 <+4>: ud2 

override func viewDidLoad() {
    super.viewDidLoad()
    do {
      let batchResult = try coreDataStack.managedContext.execute(batchUpdate) as! NSBatchUpdateResult
      print("Records updated \(batchResult.result!)")
    } catch let error as NSError {
      print("Could not update \(error), \(error.userInfo)")
    }

    let venueFetchRequest: NSFetchRequest<Venue> = Venue.fetchRequest()
    fetchRequest = venueFetchRequest

    asyncFetchRequest = NSAsynchronousFetchRequest<Venue>(fetchRequest: venueFetchRequest) {
      [unowned self] (result: NSAsynchronousFetchResult) in
      guard let venues = result.finalResult else {
        return
      }

      self.venues = venues
      self.tableView.reloadData()
    }

    do {
      guard let asyncFetchRequest = asyncFetchRequest else {
        return
      }
      try coreDataStack.managedContext.execute(asyncFetchRequest)
      // Returns immediately, cancel here if you want
    } catch let error as NSError {
      print("Could not fetch \(error), \(error.userInfo)")
    }
 }

Answer 1

这是一个很好的收获。不过，我希望答案对您有所帮助。

我下载了代码并试用了它，在稍微弄乱了它之后，我很确定这是 Apple 框架中的一个错误。示例项目中的代码看起来是正确的，但并发检查还是对其进行了标记。我不知道这是因为代码实际上导致了并发违规，还是没有违规但标志有问题。

不幸的是，您所看到的只是现在发生的情况，它无法在应用程序中修复——只有 Apple 才能解决。这也是一个长期存在的问题，您可以从 this answer from a few years ago. I suggest filing a bug with Apple.

中看到

如果启用方案“-com.apple.CoreData.ConcurrencyDebug 1”，为什么 raywenderlich 代码会中断

Why does the raywenderlich code break if you enable the scheme "-com. apple.CoreData.ConcurrencyDebug 1"

core-data

nsfetchrequest

nsmanagedobjectcontext

executefetchrequest

swift