ios - 在执行 segue 之前如何检查服务器响应值

Question

这是我在 UploadModel.swift 中的代码

func uploadSpecialistWithId(login: String, password: String) {
        let requestUrl = URL(string: "http://localhost:3000/api/register/specialist")!
        var request = URLRequest(url: requestUrl)
        request.httpMethod = "POST"
        let postParams = "login=\(login)&password=\(password)"
        print(postParams)
        request.httpBody = postParams.data(using: String.Encoding.utf8)
        let task = URLSession.shared.dataTask(with: request) {(data, response, error)
            in
            if(error != nil) {
                print("error -> \(error!.localizedDescription)")
            } else {
                print("data uploaded")
                self.parseJSONSpecialistResponse(data: data!)
            }

        }
        task.resume()
    }

    func parseJSONSpecialistResponse(data: Data) {

        var jsonResult = NSDictionary()
        let specialist = Specialist()
        do {
            jsonResult = try JSONSerialization.jsonObject(with: data, options: .allowFragments) as! NSDictionary
        } catch let error as NSError {
            print("error -> \(error.localizedDescription)")
        }

        let items = NSMutableArray()

        if let login = jsonResult["login"] as? String,
            let specialistId = jsonResult["_id"] as? String {
            specialist.login = login
            specialist.specialistId = specialistId
            print("Added \(specialist.itemDescribtion())")
            items.add(specialist)
        } else {
            let errorCode = jsonResult["code"] as! Int
            print("Erorr with code -> \(errorCode)")
            items.add(errorCode)
        }

        DispatchQueue.main.async(execute: { () -> Void in
            self.delegate.itemsUploaded(items: items)
        })
    }

但是当我尝试使用现有登录名注册专家时，segue 在我处理服务器响应之前就已经执行了。我应该改变什么来解决这个问题？这是我在 ViewController.swift 中的代码

func itemsUploaded(items: NSArray) {
        if let errorCode = items[0] as? Int {
            if errorCode == 11000 {
                warningLabel.text = "This login is already used"
                error = true
            }
        }
        if let specialist = items[0] as? Specialist {
            self.specialistId = specialist.specialistId!
            print("Value after itemsUploaded --> \(self.specialistId)")
        }
    }

    @IBAction func doneButtonTouched(_ sender: Any) {
        uploadModel.uploadSpecialistWithId(login: loginTextField.text!, password: passwordTextField.text!)
        if(error == false) {
            print("Segue perform value -> \(specialistId)")
            performSegue(withIdentifier: "regToRegCompleteSegue", sender: self)
        }
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        let destination = segue.destination as! RegistrationCompleteViewController
        print("Segue prepare value -> \(specialistId)")
        destination.specialistId = self.specialistId
    }

据我了解，由于 dataTask 异步，我遇到了此问题。但是为什么当 self.delegate 已经在主队列中时它不起作用？

编辑:添加completionHandler并没有解决我的问题，但卡姆兰的提议正在发挥作用。

Answer 1

完成响应后，您应该通过移动 itemsUploaded 中的以下行来执行 segue，如下所示，

@IBAction func doneButtonTouched(_ sender: Any) {
     uploadModel.uploadSpecialistWithId(login: logiTextField.text!, password: passwordTextField.text!)
 }

func itemsUploaded(items: NSArray) {
      if let errorCode = items[0] as? Int {
          if errorCode == 11000 {
              warningLabel.text = "This login is already used"
              error = true
          }
       }
       if let specialist = items[0] as? Specialist {
           self.specialistId = specialist.specialistId!
           print("Value after itemsUploaded --> \(self.specialistId)")
       }

      if(error == false) {
           print("Segue perform value -> \(specialistId)")
           performSegue(withIdentifier: "regToRegCompleteSegue", sender: self)
      }
}