Objective c 快速编程

我是swift语言的初学者。我得到这个错误：

Error: Any object does not have member named subscript.

有人能给出解决办法吗

我的代码：

        controller! = UIAlertController(title: "Welcome", message: "Hi...", preferredStyle: .Alert)

        let action = UIAlertAction(title: "Please enter atleat 10 characters", style: UIAlertActionStyle.Default, handler: {[weak self] (paramAction:UIAlertAction!) in

            let userName = self!.controller!.textFields[0].text
            println("your username is \(userName)")
        })

        controller!.addTextFieldWithConfigurationHandler({(textField:UITextField!) in
            textField.placeholder = "XXXXX-XXXXX"
        })

用这个

var controller = UIAlertController(title: "Welcome", message: "Hi...", preferredStyle: UIAlertControllerStyle.Alert)

        let action = UIAlertAction(title: "Please enter atleat 10 characters", style: UIAlertActionStyle.Default, handler: {[weak self] (paramAction:UIAlertAction!) in

            var userName = controller.textFields?
            println("your username is \(userName)")
        })
        controller.addTextFieldWithConfigurationHandler({(textField:UITextField!) in
            textField.placeholder = "XXXXX-XXXXX"
        })
        controller.view.center = self.view.center
        self.view .addSubview(controller.view)

---

如何声明变量

textFields

？实际上，该代码在cook book中。我只是打字。我犯了那个错误。。你能给出一个正确的代码吗？？

let action = UIAlertAction(title: "Next", style: UIAlertActionStyle.Default, handler: {[weak self](paramAction:UIAlertAction!) in
                if let textFields = self!.controller?.textFields{
                let theTextFields = textFields as [UITextField]
                let userName = theTextFields[0].text
                println("Your username is \(userName)")
            }

        })