dispatchqueue in swift 3 appears as unresolved identifier [duplicate]

Question

I am trying to take/record video asynchronously on the main thread. However, when I call dispatch.main.async, I always get the error:

use of unresolved identifier DispatchQueue

I've looked everywhere from WWDC to Apple's Documentation, but I see no evidence of the type being deprecated.

Here is the code:

   if !self.cameraEngine.isRecording {
            if let url = CameraEngineFileManager.temporaryPath("video.mp4") {
                self.cameraButton.setTitle("stop recording", forState: [])
                self.cameraEngine.startRecordingVideo(url, blockCompletion: { (url: NSURL?, error: NSError?) -> (Void) in
                    if let url = url {

                        DispatchQueue.main.async {
                            self.cameraButton.setTitle("start recording", for: .normal)
                            CameraEngineFileManager.saveVideo(url, blockCompletion: { (success: Bool, error: Error?) -> (Void) in
                                if success {
                                    let alertController =  UIAlertController(title: "Success, video saved !", message: nil, preferredStyle: .alert)
                                    alertController.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
                                    self.present(alertController, animated: true, completion: nil)
                                }
                            })
                        }
                    }
                })
            }
        }
        else {
            self.cameraEngine.stopRecordingVideo()
        }
    }

Answer 1

You can either put

import Foundation 

or

import Dispatch

at the beginning of your code to start using DispatchQueue class without any issue.