在 URLSession.shared.dataTask(with: url) 中执行SegueWithIdentifier

Question

如果用户已注册，我正在测试服务器上进行检查。如果服务器返回，用户名和密码为真，我想使用标识符“登录”执行 Segue。如果我将 performeSegue 放在 URLSession dataTask 中，程序会因以下错误而崩溃：“以 NSException 类型的未捕获异常终止” 我不知道该怎么办。由于 resume() 函数，我不能将 performSegue 放在 dataTask 之外。它会在我从服务器获取数据之前执行。

这是我的代码：

@IBAction func login(_ sender: AnyObject) {
    var session:String?

    if userName.text!.isEmpty || logInPassword.text!.isEmpty{
        let noUserName = UIAlertController(title: "Kein Benutzername oder Passwort", message: "Bitte geben sie einen Benutzernamen und ein Passwort ein.", preferredStyle: .alert)
        noUserName.addAction(OKAction)
        self.present(noUserName, animated: true)
    } else {
        //Implementing URLSession
        let urlString = "http://www.***.me/playground/api/v1/user/login/\(userName.text!)/\(logInPassword.text!)"
        guard let url = URL(string: urlString) else {
            print("Error: couldn't open link")
            return
        }

        URLSession.shared.dataTask(with: url) { (data, response, error) in
            guard let responseData = data else {
                print("Error: did not receive data")
                return
            }

            //Implement JSON decoding and parsing
            do {
                //Decode retrived data with JSONDecoder and assing type of Article object
                let personsData = try JSONDecoder().decode(LoginTest.self, from: responseData)
                session = personsData.session
                dump(personsData)

            } catch let jsonError {
                print("Error: \(jsonError)")

            }

            if session != nil{
                //loging in
                print("now loged in")
                self.performSegue(withIdentifier: "Login", sender: self)
                //here it crashes

            } else {
                let alertWrongPassword = UIAlertController(title: "Benutzername und Passwort stimmen nicht überein", message: "Bitte versuchen Sie es erneut.", preferredStyle: .alert)
                alertWrongPassword.addAction(self.OKAction)
                self.present(alertWrongPassword, animated: true)
            }
        }.resume()
        //End implementing URLSession
    }
}

Answer 1

根据异常原因，你必须在主线程上执行 segue

DispatchQueue.main.async {
    self.performSegue(withIdentifier: "Login", sender: self)
}