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在尝试向我的控制器添加例程以在用户的​​计算机上搜索具有指定用户（Mavericks+）标签的用户文件后，我束手无策。我遇到了一个搜索将开始的块，但没有返回结果并且操作队列为零。

这是代码：

class myController: NSWindowController {

    //define metadataQuery 
    var metadataQuery: NSMetadataQuery!
    var metadataQueryDidUpdateObserver: AnyObject?
    var metadataQueryDidFinishGatheringObserver: AnyObject?

    //initialize notificationsCenter
    let notificationsCenter = NotificationCenter.default

func doSpotlightSearch(){

    //add observers
    notificationsCenter.addObserver(self, selector: "initalGatherComplete:", name: NSNotification.Name.NSMetadataQueryDidFinishGathering, object: nil)
    notificationsCenter.addObserver(self, selector: "batchReturned:", name: NSNotification.Name.NSMetadataQueryDidUpdate, object: nil)


    metadataQuery = NSMetadataQuery()
    metadataQuery.searchScopes = [NSMetadataQueryIndexedLocalComputerScope]
    metadataQuery.predicate = NSPredicate(format: "kMDItemUserTags == 'myTags.testTag'")

    //start search
    metadataQuery.start()

    //test to see if query is up and running
    while metadataQuery.isGathering{
        print(metadataQuery.operationQueue?.operationCount)
        print ("result count: \(metadataQuery.resultCount)")
        sleep(1)
    }

func batchReturned(_ sender: NSNotification) {
    print("Running batchReturned func")

    let resultCounter = metadataQuery.resultCount
    print("Number of results:\(resultCounter)")
    let notificationsCenter = NotificationCenter.default

    notificationsCenter.removeObserver(self, name: NSNotification.Name.NSMetadataQueryDidFinishGathering, object: nil)
}

func initalGatherComplete(_ sender: NSNotification) {
    print("Running initialGatherComplete func")

    metadataQuery.stop()
    let resultCounter = metadataQuery.resultCount
    print("Number of results:\(resultCounter)")
    let notificationsCenter = NotificationCenter.default
    notificationsCenter.removeObserver(self, name: NSNotification.Name.NSMetadataQueryDidFinishGathering, object: nil)
}

当我运行上面的代码时，它显示结果队列为零，结果计数为零。即使我取出 isGathering 循环，batchReturned 和 initialGatherComplete 函数也不会被调用。

我怀疑谓词格式可能存在问题，但是当我使用 mdfind 将查询放入终端时，这可以正常工作。

4

1 回答 1

1

从NSMetadataQuery.start()方法的文档：This method must be called from the receiver’s operationQueue or on the main thread.

如果您没有start()从主线程调用方法，您有责任创建OperationQueue自己并从那里开始，例如：

// Declare on class-level
private lazy var queryOperationQueue: OperationQueue = {
  let queue = OperationQueue()
  queue.maxConcurrentOperationCount = 1 // restriction for NSMetadataQuery
  return queue
}()


...

func doSpotlightSearch() {
  metadataQuery = NSMetadataQuery()
  metadataQuery.searchScopes = [NSMetadataQueryIndexedLocalComputerScope]
  metadataQuery.predicate = NSPredicate(format: "kMDItemUserTags == 'myTags.testTag'")

  // assign queue to NSMetadataQuery
  metadataQuery.operationQueue = queryOperationQueue

  // run query from its queue
  metadataQuery.operationQueue?.addOperation {
    metadataQuery.start()
  }
}

希望很清楚。

于 2020-11-24T14:37:48.997 回答