swift - UIAlertController 的用法

ios 8 以后苹果官方建议使用UIAlertController这个类，所以专门去网上找资料，了解了下用法，

1、创建一个alertController

let alertController = UIAlertController(title: "系统提示",
            message: "您确定要离开吗？", preferredStyle: .alert)
        let cancelAction = UIAlertAction(title: "取消", style: .cancel, handler: nil)
        let okAction = UIAlertAction(title: "好的", style: .default,
            handler: {
                action in
                print("点击了确定")
        })
        alertController.addAction(cancelAction)
        alertController.addAction(okAction)
        self.present(alertController, animated: true, completion: {
　　　　
　　　　　　　　//这里可以做一些其他操作
　　　　})

2、创建一个actionSheet

（注：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，不管添加的次序是如何）

let alertController = UIAlertController(title: "保存或删除数据", message: "删除数据将不可恢复",
    preferredStyle: .actionSheet)
let cancelAction = UIAlertAction(title: "取消", style: .cancel, handler: nil)
let deleteAction = UIAlertAction(title: "删除", style: .destructive, handler: nil)
let archiveAction = UIAlertAction(title: "保存", style: .default, handler: nil)
alertController.addAction(cancelAction)
alertController.addAction(deleteAction)
alertController.addAction(archiveAction)
self.present(alertController, animated: true, completion: nil)

3、按钮使用警告模式，文字颜色变化，用来警示用户

var okAction = UIAlertAction(title: "好的", style: .destructive, handler: nil)

4、添加任意数量的文本输入框

 let myAlertController = UIAlertController(title:"系统登录",message:"请输入用户名和密码",preferredStyle:.alert)
        myAlertController.addTextField { (textField:UITextField) in
            textField.placeholder = "用户名"
        }

        myAlertController.addTextField { (textField:UITextField) in
            textField.placeholder = "密码"
            textField.isSecureTextEntry = true
        }

        myAlertController.addTextField { (textField:UITextField) in
            textField.placeholder = "重复密码"
            textField.isSecureTextEntry = true
        }

        let cancelAction = UIAlertAction(title:"取消",style:.cancel,handler:nil)
        let okAction = UIAlertAction(title:"确定",style:.default,
               handler:{
                action in
                let login = myAlertController.textFields?.first
                let passWord = myAlertController.textFields?.last
                print("用户名是：\(String(describing: login)) 密码是：\(String(describing: passWord))")
        })

        myAlertController.addAction(cancelAction)
        myAlertController.addAction(okAction)
        self.present(myAlertController, animated: true) {
            self.view.backgroundColor = UIColor.blue
        }

如图

5、使用代码移除提示框

self.dismiss(animated: true) {
          //其他操作
}