使用UIAlertController：

let alertController = UIAlertController(title: "title", message: nil, preferredStyle: .Alert)
alertController.addTextFieldWithConfigurationHandler { (textField) -> Void in }
alertController.addAction(UIAlertAction(title: "cancel", style: UIAlertActionStyle.Cancel, handler: nil))
logInAlertController.addAction(UIAlertAction(title: "go", style: UIAlertActionStyle.Default, handler: { (action) -> Void in }

雨燕四号
这听起来像是在呈现控制器而不是在用户选择警报操作时进行完成处理。
您可以尝试以下操作：

import UIKit

class MyViewController: UIViewController
{
    var someStringVariable:String = ""

    func presentAnAlert()
    {
        let alert = UIAlertController(
                title: "Title",
                message: "Message",
                preferredStyle: .actionSheet //choose which style you prefer
        )

        alert.addTextField()
        { (textField) in
            //this is for configuring the text field the user will see
            textField.borderStyle = UITextField.BorderStyle.bezel
        }

        alert.addAction(UIAlertAction(title: "OK", style: .default)
        { action in
            //use this space to transfer any data
            let textField = alert.textFields![0]
            self.someStringVariable = textField.text ?? ""
        })

        self.present(alert, animated: true)
        {
            //this will run once the action of**presenting**the view
            //is complete, rather than when the presented view has been
            //dismissed
        }
    }

    override viewDidLoad()
    {
        super.viewDidLoad()
        self.presentAnAlert()
        print(self.someStringVariable)
        //prints whatever the user input before pressing the OK button
    }
}

我希望这对你有帮助！