ios - 等待函数在 Swift 中结束

Question

我有一个使用 json 获取数据的函数，我将所有数据附加到一个数组中。我尝试创建信号量并等到向信号量发送信号以继续但它不起作用(我不确定我是否正确)，然后我在 Stackoverflow 中看到一个问题，答案是创建一个完成处理程序像那样

func application(application: UIApplication!, performFetchWithCompletionHandler completionHandler: ((UIBackgroundFetchResult) -> Void)!) {
    getUrunGrup(completionHandler)
}

所以我改变了我的功能

func getUrunGrup(completionHandler: ((UIBackgroundFetchResult) -> Void)!){
    Alamofire.request(.GET, "http://213.136.86.160:27701/Thunder/DataService/GetUrunGrup")
        .responseJSON {(request, response, jsonObj, error) in
            if let jsonresult:NSDictionary = jsonObj as? NSDictionary{
                if let result: AnyObject = jsonresult["Result"] {
                    let elementCount = result.count
                    for (var i = 0; i<elementCount; ++i){
                        if let name: AnyObject = result[i]["Adi"]!{
                            if let kod:AnyObject = result[i]["Kod"]!{
                                urunUstGrup.append(["Adi": "\(name)", "Kod": "\(kod)"])
                                println("getUrunGrup \(i)")


                                }
                            }
                        }
                    }
                }

            }
    completionHandler(UIBackgroundFetchResult.NewData)
    println("Background Fetch Complete")

    }

但是没有关于我应该如何调用这个函数的答案？

Answer 1

您必须将异步函数传递给稍后调用的处理程序，如下所示:

func application(application: UIApplication!, performFetchWithCompletionHandler completionHandler: ((UIBackgroundFetchResult) -> Void)!) {
    loadShows(completionHandler)
}

func loadShows(completionHandler: ((UIBackgroundFetchResult) -> Void)!) {
    //....
    //DO IT
    //....

    completionHandler(UIBackgroundFetchResult.NewData)
    println("Background Fetch Complete")
}

或(更清洁的方式恕我直言)

添加一个中间的completionHandler

func application(application: UIApplication!, performFetchWithCompletionHandler completionHandler: ((UIBackgroundFetchResult) -> Void)!) {
    loadShows() {
        completionHandler(UIBackgroundFetchResult.NewData)
        println("Background Fetch Complete")
    }
}

func loadShows(completionHandler: (() -> Void)!) {
    //....
    //DO IT
    //....
    completionHandler()
}