您应该添加自己的
completionHandler闭包参数，并在任务完成时调用它：
func googleDuration(origin: String, destination: String, completionHandler: (Int?, NSError?) -> Void ) -> NSURLSessionTask { // do calculations origin and destiantion with google distance matrix api let originFix = origin.stringByReplacingOccurrencesOfString(" ", withString: "+", options: NSStringCompareOptions.LiteralSearch, range: nil); let destinationFix = destination.stringByReplacingOccurrencesOfString(" ", withString: "+", options: NSStringCompareOptions.LiteralSearch, range: nil); let urlAsString = "https://maps.googleapis.com/maps/api/distancematrix/json?origins="+originFix+"&destinations="+destinationFix println(urlAsString) let url = NSURL(string: urlAsString)! let urlSession = NSURLSession.sharedSession() let task = urlSession.dataTaskWithURL(url) { data, response, error -> Void in if error != nil { // If there is an error in the web request, print it to the console // println(error.localizedDescription) completionHandler(nil, error) return } //println("parsing JSON"); let json = JSON(data: data) if (json["status"].stringValue == "OK") { if let totalTime = json["rows"][0]["elements"][0]["duration"]["value"].integerValue { // println(totalTime); completionHandler(totalTime, nil) return } let totalTimeError = NSError(domain: kAppDomain, pre: kTotalTimeError, userInfo: nil) // populate this any way you prefer completionHandler(nil, totalTimeError) } let jsonError = NSError(domain: kAppDomain, pre: kJsonError, userInfo: nil) // again, populate this as you prefer completionHandler(nil, jsonError) } task.resume() return task}NSURLSessionTask如果调用者希望能够取消任务，我也将获得此返回。
无论如何，您可以这样称呼它：
googleDuration(origin, destination: destination) { totalTime, error in if let totalTime = totalTime { // use totalTime here } else { // handle error }}
