ios - 核心数据崩溃: EXC_BAD_ACCESS while trying access data got using predicate

Question

我将值保存到实体方法，该方法保存新数据并更新现有数据。

func saveSteps(_ serverJson: [[String: Any]]){
   let stepService = StepService(context: context);
   if(serverJson.count > 0){
     for step in serverJson {
       let stepTitle = step["stepTitle"] as? String ?? ""
       let stepDescription = step["stepDescription"] as? String ?? ""
       let stepId = step["_id"] as? String ?? ""
       let predicate: NSPredicate = NSPredicate(format: "stepId=%@", stepId)
       let stepList = stepService.get(withPredicate: predicate);
       if(stepList.count == 0){
         stepService.create(stepId: stepId, stepTitle: stepTitle, stepDescription: stepDescription);
       }else{
         if let updatableStep = stepList.first{
           updatableStep.stepDescription = stepDescription //EXC_BAD_ACCESS Error Here
           updatableStep.stepName = stepName
           updatableStep.stepTitle = stepTitle
           stepService.update(updatedStep: updatableStep)
      }else{
        stepService.create(stepId: stepId, stepTitle: stepTitle, stepDescription: stepDescription);
      }
  }


    saveContext()
}

我的Create更新和获取方法在stepService中

func create(stepId:String, stepDescription: String, stepTitle:String){
   let newItem = NSEntityDescription.insertNewObject(forEntityName: "Steps", into: context) as! Steps //EXC_BAD_ACCESS Error Here
    newItem.stepId = stepId
    newItem.stepTitle = stepTitle
    newItem.stepDescription = stepDescription
}
func update(updatedStep: Steps){
  if let step = getById(id: updatedStep.objectID){
     step.stepId = updatedStep.stepId
     step.stepTitle = updatedStep.stepTitle
     step.stepDescription = updatedStep.stepDescription
}
func get(withPredicate queryPredicate: NSPredicate) -> [Steps]{
 let fetchRequest: NSFetchRequest<Steps> = Steps.fetchRequest()

    fetchRequest.returnsObjectsAsFaults = false
    fetchRequest.predicate = queryPredicate

    do {
        let response = try context.fetch(fetchRequest)
        return response

        } catch let error as NSError {
            // failure
            print(error)
            return [Steps]()
        }
    }
}

Mysave 上下文方法是

// Creating private queue to save the data to disk
    lazy var savingModelcontext:NSManagedObjectContext = {
        var managedObjectContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
        managedObjectContext.persistentStoreCoordinator = self.coordinator

        return managedObjectContext
    }()

    // Creating Context to save in block main queue this will be temporary save
    lazy var context:NSManagedObjectContext = {
        var managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
        managedObjectContext.parent = self.savingModelcontext

        return managedObjectContext
    }()

func saveContext () {
    guard savingModelcontext.hasChanges || context.hasChanges else {
        return
    }

    context.performAndWait {
        do {
            try self.context.save()
        } catch let error as NSError {
            print("Could not save in Context: \(error.localizedDescription)")
        }
    }

    savingModelcontext.perform {
        do {
            try self.savingModelcontext.save()
        } catch let error as NSError {
            print("Could not save savingModelContext: \(error.localizedDescription)")
        }
    }
}

有两个地方核心数据崩溃并显示相同的错误消息，一个是当我访问数据以更新方法时，另一个是当我尝试使用带有实体名称的 NSEntityDescription.insertNewObject 创建新项目时。虽然我已经尝试过使用 userInitiated 和默认的 qos 调度队列。我没有使用背景，因为用户可能会打开一些可能使用它的东西。

问题是崩溃不一致，并且在进行调试时从未崩溃，这让我相信这是并发问题，但更新时数据从未被删除或读取。

PS:我已经阅读了具有相同和相似问题的问题，但我无法在这里得到有效的答案。

如果我有什么错误，请指出

感谢任何帮助

Answer 1

崩溃的原因是我试图更改，因为我正在主线程中使用私有(private)队列上下文，反之亦然。使用组调度队列来修复此问题，该队列具有专用队列上下文所需的 QOS 和使用主队列对象的主线程。