UIAlertAction 的写入处理程序

我向用户展示了一个 UIAlertView，但我不知道如何编写处理程序。这是我的尝试:

let alert = UIAlertController(title: "Title",
message: "Message",
preferredStyle: UIAlertControllerStyle.Alert)


alert.addAction(UIAlertAction(title: "Okay",
style: UIAlertActionStyle.Default,
handler: {self in println("Foo")})

我在 Xcode 有很多问题。

文件上说是 convenience init(title title: String!, style style: UIAlertActionStyle, handler handler: ((UIAlertAction!) -> Void)!)

整个街区/关闭现在有点超出我的能力范围。任何建议都非常感谢。

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最佳答案

Instead of self in your handler, put (alert: UIAlertAction!). This should make your code look like this 

    alert.addAction(UIAlertAction(title: "Okay",
style: UIAlertActionStyle.Default,
handler: {(alert: UIAlertAction!) in println("Foo")}))

this is the proper way to define handlers in Swift.

As Brian pointed out below, there are also easier ways to define these handlers. Using his methods is discussed in the book, look at the section titled Closures

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Functions are first-class objects in Swift. So if you don't want to use a closure, you can also just define a function with the appropriate signature and then pass it as the handler argument. Observe:

func someHandler(alert: UIAlertAction!) {
// Do something...
}


alert.addAction(UIAlertAction(title: "Okay",
style: UIAlertActionStyle.Default,
handler: someHandler))
小开

Lets assume that you want an UIAlertAction with main title, two actions (save and discard) and cancel button:

let actionSheetController = UIAlertController (title: "My Action Title", message: "", preferredStyle: UIAlertControllerStyle.ActionSheet)


//Add Cancel-Action
actionSheetController.addAction(UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel, handler: nil))


//Add Save-Action
actionSheetController.addAction(UIAlertAction(title: "Save", style: UIAlertActionStyle.Default, handler: { (actionSheetController) -> Void in
print("handle Save action...")
}))


//Add Discard-Action
actionSheetController.addAction(UIAlertAction(title: "Discard", style: UIAlertActionStyle.Default, handler: { (actionSheetController) -> Void in
print("handle Discard action ...")
}))


//present actionSheetController
presentViewController(actionSheetController, animated: true, completion: nil)

This works for swift 2 (Xcode Version 7.0 beta 3)

小开

You can do it as simple as this using swift 2:

let alertController = UIAlertController(title: "iOScreator", message:
"Hello, world!", preferredStyle: UIAlertControllerStyle.Alert)
alertController.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Destructive,handler: { action in
self.pressed()
}))


func pressed()
{
print("you pressed")
}


**or**




let alertController = UIAlertController(title: "iOScreator", message:
"Hello, world!", preferredStyle: UIAlertControllerStyle.Alert)
alertController.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.Destructive,handler: { action in
print("pressed")
}))

All the answers above are correct i am just showing another way that can be done.

小开

this is how i do it with xcode 7.3.1

// create function
func sayhi(){
print("hello")
}

// create the button 

let sayinghi = UIAlertAction(title: "More", style: UIAlertActionStyle.Default, handler:  { action in
self.sayhi()})

// adding the button to the alert control

myAlert.addAction(sayhi);

// the whole code, this code will add 2 buttons 

  @IBAction func sayhi(sender: AnyObject) {
let myAlert = UIAlertController(title: "Alert", message:"sup", preferredStyle: UIAlertControllerStyle.Alert);
let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler:nil)


let sayhi = UIAlertAction(title: "say hi", style: UIAlertActionStyle.Default, handler:  { action in
self.sayhi()})


// this action can add to more button
myAlert.addAction(okAction);
myAlert.addAction(sayhi);


self.presentViewController(myAlert, animated: true, completion: nil)
}


func sayhi(){
// move to tabbarcontroller
print("hello")
}
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Syntax change in swift 3.0

alert.addAction(UIAlertAction(title: "Okay",
style: .default,
handler: { _ in print("Foo") } ))
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create alert, tested in xcode 9

let alert = UIAlertController(title: "title", message: "message", preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: self.finishAlert))
self.present(alert, animated: true, completion: nil)

and the function 

func finishAlert(alert: UIAlertAction!)
{
}
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In Swift 4 :

let alert=UIAlertController(title:"someAlert", message: "someMessage", preferredStyle:UIAlertControllerStyle.alert )


alert.addAction(UIAlertAction(title: "ok", style: UIAlertActionStyle.default, handler: {
_ in print("FOO ")
}))


present(alert, animated: true, completion: nil)
小开

  1. In Swift

    let alertController = UIAlertController(title:"Title", message: "Message", preferredStyle:.alert)


let Action = UIAlertAction.init(title: "Ok", style: .default) { (UIAlertAction) in
// Write Your code Here
}


alertController.addAction(Action)
self.present(alertController, animated: true, completion: nil)

  2. In Objective C

    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Title" message:@"Message" preferredStyle:UIAlertControllerStyleAlert];


UIAlertAction *OK = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action)
{
}];


[alertController addAction:OK];


[self presentViewController:alertController animated:YES completion:nil];
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In Swift 5, here's what you can also do:

let handler = { (action: UIAlertAction!) -> Void in
//do tasks
}

Then when you are making the action, just substitute it in like this:

let action = UIAlertAction(title: "Do it", style: .default, handler: handler)

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