Swift - 警告提示框（UIAlertController）的用法

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
super.viewDidLoad()
}

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
// 创建
let alertController = UIAlertController(title: "提示", message: "你确定要离开？", preferredStyle:.Alert)

// 设置2个UIAlertAction
let cancelAction = UIAlertAction(title: "取消", style: .Cancel, handler: nil)
let okAction = UIAlertAction(title: "好的", style: .Default) { (UIAlertAction) in
print("点击了好的")
}

// 添加
alertController.addAction(cancelAction)
alertController.addAction(okAction)

// 弹出
self.presentViewController(alertController, animated: true, completion: nil)
}
}

// 除了弹出，还可以使用底部向上滑出的样式
// 注意：如果上拉菜单中有『取消』按钮的话，那么它永远都会出现在菜单的底部，不管添加的次序如何

// 创建
// preferredStyle 为 ActionSheet
let alertController = UIAlertController(title: "保存或删除数据", message: "删除数据将不可恢复", preferredStyle:.ActionSheet)

// 设置2个UIAlertAction
let cancelAction = UIAlertAction(title: "取消", style: .Cancel, handler: nil)
let deleteAction = UIAlertAction(title: "删除", style: .Destructive, handler: nil)
let saveAction = UIAlertAction(title: "保存", style: .Default, handler: nil)

// 添加到UIAlertController
alertController.addAction(cancelAction)
alertController.addAction(saveAction)
alertController.addAction(deleteAction)

// 弹出
self.presentViewController(alertController, animated: true, completion: nil)

/*
添加任意数量的文本输入框（比如可以用来实现登录框）
*/

let alertController = UIAlertController(title: "系统登录", message: "请输入用户名和密码", preferredStyle: UIAlertControllerStyle.Alert)

alertController.addTextFieldWithConfigurationHandler { (textField:UITextField) in
textField.placeholder = "用户名"
}
alertController.addTextFieldWithConfigurationHandler { (textField:UITextField) in
textField.placeholder = "密码"
textField.secureTextEntry = true
}

let cancelAction = UIAlertAction(title: "取消", style: UIAlertActionStyle.Cancel, handler: nil)
let okAction = UIAlertAction(title: "好的", style: UIAlertActionStyle.Default) { (UIAlertAction) in
let login = alertController.textFields![0]
let pwd = alertController.textFields![1]
print("用户名：\(login.text) 密码：\(pwd.text)")
}

alertController.addAction(cancelAction)
alertController.addAction(okAction)

// 弹出
self.presentViewController(alertController, animated: true, completion: nil)