ios - 依次执行一段代码

Question

作为我正在创建的应用程序的一部分，我实现了运行跟踪功能。我有大部分代码，但我有一段代码几乎执行得太快，我需要在下一段代码执行之前从 newRun.php 脚本返回响应，这是因为它返回了一个 ID，我需要执行下一段代码。

    @IBAction func stopRun(_ sender: Any)
    {
       startButton.isHidden=false
       stopButton.isHidden=true
       saveRun()
    }

上面是运行 saveRun 的代码部分。单击此按钮，我希望它在“run_history”表中创建新记录。仅当此操作完成后，我才希望它使用 newRun.php 脚本返回的 run_id 创建新记录，其中将包括运行的所有经度和纬度。

    private func saveRun()
    {

首先执行。

    let request = NSMutableURLRequest(url: NSURL(string: "../newRun.php")! as URL)
    request.httpMethod = "POST"
    let postString = "id=\(MainMenuViewController.myVariables.user_id)"
    request.httpBody = postString.data(using: String.Encoding.utf8)



    let task = URLSession.shared.dataTask(with: request as URLRequest)
    {
        data, response, error in



        if error != nil
        {
            print("error=\(String(describing: error))")
            return
        }

        print("response = \(String(describing: response))")

        let responseString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
        MainMenuViewController.myVariables.new_run_id = responseString! as String
        print ("Run ID =\(MainMenuViewController.myVariables.new_run_id))")
    }
    task.resume()

其次执行。

    for location in self.locationList
    {
        var timestamp = location.timestamp
        var latitude:String = String(format:"%f", location.coordinate.latitude)
        var longitude:String = String(format:"%f", location.coordinate.longitude)

        print("Timestamp is \(timestamp)")
        print("latitude is \(latitude)")
        print("longitude is \(longitude)")
        let requestGps = NSMutableURLRequest(url: NSURL(string: "../newRunGps.php")! as URL)
        requestGps.httpMethod = "POST"
        let postStringGps = "id=\(MainMenuViewController.myVariables.new_run_id)&lng=\(longitude)&lat=\(latitude)&time=\(timestamp)"
        requestGps.httpBody = postStringGps.data(using: String.Encoding.utf8)

        let taskGps = URLSession.shared.dataTask(with: requestGps as URLRequest)
        {
            dataGps, responseGps, errorGps in

            if errorGps != nil
            {
                print("error=\(String(describing: errorGps))")
                return
            }

            print("response = \(String(describing: responseGps))")

            let responseStringGps = NSString(data: dataGps!, encoding: String.Encoding.utf8.rawValue)
            print ("responseString =\(responseStringGps!))")
        }
        taskGps.resume()
    }

}

我看到提到了 DispatchQueue 和 DispatchGroup，但我不确定如果有人可以帮助我解决这个问题，我将如何在我的代码中使用它们？

Answer 1

你可以尝试这样的事情:

DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(4), execute: {
                    for vc in (self.navigationController?.viewControllers ?? []) {
                        if vc is DashboardViewController {
                            self.navigationController?.popToViewController(vc, animated: true)
                            break
                        }
                    }
                })