ios – swift 3中的dispatchqueue显示为未解析的标识符

参见英文答案 > Swift 3.0 unresolved identifier for DispatchQueue2个
我试图在主线程上异步拍摄/录制视频.但是,当我调用dispatch.main.async时,我总是收到错误：

use of unresolved identifier DispatchQueue

从WWDC到Apple的文档我到处都是,但我看不到这种类型被弃用的证据.

这是代码：

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()
        }
    }

import Foundation

import Dispatch