【Swift 筆記 Draft】UIAlertController 製作

Apple 將 Alert Window 視為 ViewController， 而不是一個 View 的概念，所以以此取代 UIActionSheet 與 UIAlertView 類別。市面上若有 Swift 的書，Alert Dialog 的製作仍沿用 UIAlertView 為早期用法。

製作 Alert Dialog 的步驟如下:

1. 建立 Alert Dialog 物件 : UIAlertController
2. 建立 Alert Action 物件 : UIAlertAction
3. 將新建的 Alert Action 物件加入 Alert Dialog 物件清單 : UIAlertController.addAction
4. 顯示 Alert Dialog 物件 : UIViewController.presentViewController

以下依此步驟及Apple 的官方文件，逐步說明如何製作 Alert Dialog:


1. Declaration: UIAlertController
SWIFT
convenience init(title title: String?,
         message message: String?,
  preferredStyle preferredStyle: UIAlertControllerStyle)

寫成:

let alertController = UIAlertController(title : "My First App",
                       message : "Hello,World!",
                       preferredStyle : UIAlertControllerStyle.Alert)


2.Declaration: UIAlertAction 
SWIFT
convenience init(title title: String?,
           style style: UIAlertActionStyle,
         handler handler: ((UIAlertAction) -> Void)?)

寫成:

let alertAction = UIAlertAction(title : "OK",
                                style : UIAlertActionStyle.Default,
                                handler : nil )

3. Declaration: UIAlertController.addAction 
SWIFT
func addAction(_ action: UIAlertAction)

寫成:

alertController.addAction(alertAction)


4. Declaration: UIViewController.presentViewController
func presentViewController(_ viewControllerToPresent: UIViewController,
                  animated flag: Bool,
                completion completion: (() -> Void)?)

寫成:

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

所以，一個簡單的 Alert Dialog 完整的程式如下:



let alertController = UIAlertController(title : "My First App",
                       message : "Hello,World!",
                       preferredStyle : UIAlertControllerStyle.Alert)

let alertAction = UIAlertAction(title : "OK",
                                style : UIAlertActionStyle.Default,
                                handler : nil )

alertController.addAction(alertAction)

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




Refernce:

1. UIAlertController, https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UIAlertController_class/#//apple_ref/swift/enum/c:@E@UIAlertControllerStyle
2. UIAlertAction, https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UIAlertAction_Class/
3. UIViewController, https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UIViewController_Class/index.html#//apple_ref/occ/instm/UIViewController/presentViewController:animated:completion: