Question

当我的应用程序进入后台时（applicationDidEnterBackground之后），出现以下警告。

2015-12-11 20:54:43.661 AppName[759:124891]  *|synchronize-skip|* a fence was started inside of a snapshot block - skipping the workspace synchronize because it may dequeue messages from the fenceExemptQueue and snapshots expect that not to happen
2015-12-11 20:54:44.084 AppName[759:124891]  *|synchronize-skip|* a fence was started inside of a snapshot block - skipping the workspace synchronize because it may dequeue messages from the fenceExemptQueue and snapshots expect that not to happen

我在Google上找不到任何有关它的信息，也不知道为什么会这样。

有谁知道这意味着什么？谢谢！

Answer 1

我在Swift程序中得到了同样奇怪的错误信息，最后弄清楚我的代码出了什么问题。正确的代码是：

    override func viewDidLoad() {
    super.viewDidLoad()

    let fileMgr = NSFileManager.defaultManager()
    ubiquityURL = fileMgr.URLForUbiquityContainerIdentifier(nil)

    guard ubiquityURL != nil else {
        print("Dave: Unable to access iCloud account")
        return
    }
    ubiquityURL = ubiquityURL?.URLByAppendingPathComponent("Documents/savefile.txt")

    metaDataQuery = NSMetadataQuery()
    metaDataQuery?.predicate = NSPredicate(format: "%K like 'savefile.txt'", NSMetadataItemFSNameKey)
    metaDataQuery?.searchScopes = [NSMetadataQueryUbiquitousDocumentsScope]
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "metadataQueryDidFinishGathering:", name: NSMetadataQueryDidFinishGatheringNotification, object: metaDataQuery!)
    metaDataQuery!.startQuery()
}

在上面的代码中，正确的格式是＆＃34;％K喜欢＆＃39; savefile.txt＆＃39;＆＃34;，但是如果你忘记了文件名周围的单引号，你会得到奇怪的运行时错误消息。如果没有围绕文件名的单引号，元数据查询将无法在iCloud上找到您的文件。

Xcode中关于iOS中fenceExemptQueue的奇怪警告

1 个答案: