如何在UIAlertviewController中激活ok按钮？

Question

当我开始在UITextfield中输入文字时出现错误：
unrecognized selector sent to instance

var inputTextField: UITextField!
let alertController = UIAlertController(title: "User Name", message: "Enter your new ideatrr name", preferredStyle: .Alert)

let nextAction: UIAlertAction = UIAlertAction(title: "Update", style: .Default) { action -> Void in
        if inputTextField!.text == "" {
            println("blank text")
        }
    }

nextAction.enabled = false

let cancel = UIAlertAction(title: "Cancel", style: .Cancel) { (action) -> Void in
    alertController.addAction(nextAction)
    alertController.addAction(cancel)

    alertController.addTextFieldWithConfigurationHandler { (textField) -> Void in
        inputTextField = textField
        inputTextField.placeholder = "Enter your name"
        inputTextField.addTarget(self, action: "textFieldDidChange:", forControlEvents: UIControlEvents.EditingChanged)  
    }

    presentViewController(alertController, animated: true, completion: nil)

    func textFieldDidChange(inputTextField: UITextField!) {
        if inputTextField.text.isEmpty {
            nextAction.enabled = true
        } else {
            println("ddddd")
        }
    }
}

Answer 1

函数textFieldDidChange:需要是您正在使用的任何类的实例方法。如果将textFieldDidChange:移动到类定义中，您应该很高兴。