NSManagedObjectContext.performBlockAndWait（）在主线程/队列上运行块

print("queue1: \(NSOperationQueue.currentQueue())")
managedObjectContext.performBlockAndWait({
    print("queue2: \(NSOperationQueue.currentQueue())")
})

and output is:

和输出是:

queue1: Optional(<NSOperationQueue: 0x7fa31c030cf0>{name = 'NSOperationQueue 0x7fa31c030cf0'})
queue2: Optional(<NSOperationQueue: 0x7fa319d114d0>{name = 'NSOperationQueue Main Queue'})

So, performBlockAndWait runs the block in main thread. Don't know why? Is this the expected behaviour?

因此,performBlockAndWait在主线程中运行块。不知道为什么?这是预期的行为吗?

So, any solutions for the problems:

那么,任何问题的解决方案:

I need to run the code of the block in background, else it freezes UI. So, how can I?, or

我需要在后台运行块的代码,否则它会冻结UI。那么,我怎么样?或者

If I don't use performBlockAndWait the code in the block crash with the description Terminating app due to uncaught exception NSInvalidArgumentException, reason _referenceData64 only defined for abstract class. Any alternative?

如果我不使用performBlockAndWait块中的代码崩溃与描述终止应用程序由于未捕获的异常NSInvalidArgumentException,原因_referenceData64仅为抽象类定义。还有其他选择

2 个解决方案

#1

PerformBlock() and performBlockAndWait() runs on the queue in which your context is created. So if your managedObjectContext is created in main queue it will run in the main queue.

PerformBlock()和performBlockAndWait()在创建上下文的队列上运行。因此,如果您的managedObjectContext是在主队列中创建的,它将在主队列中运行。

If you want background execution you need to create a background context :

如果要执行后台,则需要创建后台上下文:

let privateContext = NSManagedObjectContext(
  concurrencyType: .PrivateQueueConcurrencyType)

privateContext.persistentStoreCoordinator = mainQueueContext.persistentStoreCoordinator

privateContext.performBlock {
...
}

#2

Perform your task you want to do in background in a separate function with a completion handler.

使用完成处理程序在单独的函数中执行要在后台执行的任务。

       dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
        func performFuncWithCompletion() { (Success) in
              if (Success)
                  NSOperationQueue.mainQueue().addOperationWithBlock {
                      // update UI here
                  }
               else {  
                       // Show error message?
                    }
           }  
  }


 func performFuncWithCompletion(completion : (SuccessStatus: Bool)) {
        // perform your back ground function here.
        // Decide if everything went fine
       if everythingWentFine {
           completion(true)
        }
       else {
            completion(false)
            }
}

Ask if any questions

询问是否有任何问题

#1