?yb?
2014-06-03 18:35
采纳率: 100%
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如何在 Swift 中创建一个 UIAlertView?

I have been working to create a UIAlertView in Swift, but for some reason I can't get the statement right because I'm getting this error:

Could not find an overload for 'init' that accepts the supplied arguments

Here is how I have it written:

let button2Alert: UIAlertView = UIAlertView(title: "Title", message: "message",
                     delegate: self, cancelButtonTitle: "OK", otherButtonTitles: nil)

Then to call it I'm using:

button2Alert.show()

As of right now it is crashing and I just can't seem to get the syntax right.

转载于:https://stackoverflow.com/questions/24022479/how-would-i-create-a-uialertview-in-swift

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30条回答 默认 最新

  • 旧行李 2014-06-03 18:48
    已采纳

    From the UIAlertView class:

    // UIAlertView is deprecated. Use UIAlertController with a preferredStyle of UIAlertControllerStyleAlert instead

    On iOS 8, you can do this:

    let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: UIAlertControllerStyle.Alert)
    alert.addAction(UIAlertAction(title: "Click", style: UIAlertActionStyle.Default, handler: nil))
    self.presentViewController(alert, animated: true, completion: nil)
    

    Now UIAlertController is a single class for creating and interacting with what we knew as UIAlertViews and UIActionSheets on iOS 8.

    Edit: To handle actions:

    alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: { action in
        switch action.style{
        case .Default:
            print("default")
    
        case .Cancel:
            print("cancel")
    
        case .Destructive:
            print("destructive")
        }
    }}))
    

    Edit for Swift 3:

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

    Edit for Swift 4:

    let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: UIAlertControllerStyle.alert)
    alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { action in
          switch action.style{
          case .default:
                print("default")
    
          case .cancel:
                print("cancel")
    
          case .destructive:
                print("destructive")
    
    
    }}))
    self.present(alert, animated: true, completion: nil)
    
    已采纳该答案
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  • 七度&光 2014-06-03 18:52

    You can create a UIAlert using the standard constructor, but the 'legacy' one seems to not work:

    let alert = UIAlertView()
    alert.title = "Alert"
    alert.message = "Here's a message"
    alert.addButtonWithTitle("Understood")
    alert.show()
    
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  • 胖鸭 2014-06-03 19:05

    I found this one,

    var alertView = UIAlertView();
    alertView.addButtonWithTitle("Ok");
    alertView.title = "title";
    alertView.message = "message";
    alertView.show();
    

    not good though, but it works :)

    Update:

    but I have found on header file as:

    extension UIAlertView {
        convenience init(title: String, message: String, delegate: UIAlertViewDelegate?, cancelButtonTitle: String?, otherButtonTitles firstButtonTitle: String, _ moreButtonTitles: String...)
    }
    

    somebody may can explain this.

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  • derek5. 2014-06-28 08:49

    The reason it doesn't work because some value you passed to the function isn't correct. swift doesn't like Objective-C, you can put nil to arguments which are class type without any restriction(might be). Argument otherButtonTitles is defined as non-optional which its type do not have (?)at its end. so you must pass a concrete value to it.

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  • elliott.david 2014-09-03 12:53

    Show UIAlertView in swift language :-

    Protocol UIAlertViewDelegate

    let alert = UIAlertView(title: "alertView", message: "This is alertView", delegate:self, cancelButtonTitle:"Cancel", otherButtonTitles: "Done", "Delete")
    alert.show()
    

    Show UIAlertViewController in swift language :-

    let alert = UIAlertController(title: "Error", message: "Enter data in Text fields", preferredStyle: UIAlertControllerStyle.Alert)
    alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
    self.presentViewController(alert, animated: true, completion: nil)
    
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  • from.. 2014-10-13 22:55
    @IBAction func Alert(sender: UIButton) {
    
        var alertView:UIAlertView = UIAlertView()
        alertView.title = "Alert!"
        alertView.message = "Message"
        alertView.delegate = self
        alertView.addButtonWithTitle("OK")
    
        alertView.show()
    
    }
    

    Try this

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  • python小菜 2014-12-22 14:51

    Simply do not provide otherButtonTitles in the constructor.

    let alertView = UIAlertView(title: "Oops!", message: "Something
    happened...", delegate: nil, cancelButtonTitle: "OK")
    
    alertView.show()
    

    But I do agree with Oscar, this class is deprecated in iOS 8, so there won't be no use of UIAlertView if you're doing an iOS 8 only app. Otherwise the code above will work.

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  • ~Onlooker 2015-01-13 21:14

    If you're targeting iOS 7 and 8, you need something like this to make sure you're using the right method for each version, because UIAlertView is deprecated in iOS 8, but UIAlertController is not available in iOS 7:

    func alert(title: String, message: String) {
        if let getModernAlert: AnyClass = NSClassFromString("UIAlertController") { // iOS 8
            let myAlert: UIAlertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
            myAlert.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
            self.presentViewController(myAlert, animated: true, completion: nil)
        } else { // iOS 7
            let alert: UIAlertView = UIAlertView()
            alert.delegate = self
    
            alert.title = title
            alert.message = message
            alert.addButtonWithTitle("OK")
    
            alert.show()
        }
    }
    
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  • ?yb? 2015-04-25 06:51

    Here is a funny example in Swift:

    private func presentRandomJoke() {
      if let randomJoke: String = jokesController.randomJoke() {
        let alertController: UIAlertController = UIAlertController(title:nil, message:randomJoke, preferredStyle: UIAlertControllerStyle.Alert)
        alertController.addAction(UIAlertAction(title:"Done", style:UIAlertActionStyle.Default, handler:nil))
        presentViewController(alertController, animated:true, completion:nil)
      }
    }
    
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  • MAO-EYE 2015-05-10 16:15

    Click of View

    @IBAction func testClick(sender: UIButton) {
    
      var uiAlert = UIAlertController(title: "Title", message: "Message", preferredStyle: UIAlertControllerStyle.Alert)
      self.presentViewController(uiAlert, animated: true, completion: nil)
    
      uiAlert.addAction(UIAlertAction(title: "Ok", style: .Default, handler: { action in
       println("Click of default button")
      }))
    
      uiAlert.addAction(UIAlertAction(title: "Cancel", style: .Cancel, handler: { action in
       println("Click of cancel button")
      }))
    
    }
    

    Done with two buttons OK & Cancel

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  •     class Preview: UIViewController , UIAlertViewDelegate
        {
            @IBAction func MoreBtnClicked(sender: AnyObject)
            {
                var moreAlert=UIAlertView(title: "Photo", message: "", delegate: self, cancelButtonTitle: "No Thanks!", otherButtonTitles: "Save Image", "Email", "Facebook", "Whatsapp" )
                moreAlert.show()
                moreAlert.tag=111;
            }
    
            func alertView(alertView: UIAlertView, didDismissWithButtonIndex buttonIndex: Int)
            {
                if alertView.tag==111
                {
                    if buttonIndex==0
                    {
                        println("No Thanks!")
                    }
                    else if buttonIndex==1
                    {
                        println("Save Image")
                    }
                    else if buttonIndex == 2
                    {
                        println("Email")
                    }
                    else if buttonIndex == 3
                    {
                        println("Facebook")
                    }
                    else if buttonIndex == 4
                    {
                        println("Whatsapp")
                    }
                }
            }
        }
    
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  • ~Onlooker 2015-07-14 07:44

    I got the following UIAlertView initialization code to compile without errors (I thing the last, varyadic part is tricky perhaps). But I had to make sure the class of self (which I am passing as the delegate) was adopting the UIAlertViewDelegate protocol for the compile errors to go away:

    let alertView = UIAlertView(
                      title: "My Title",
                      message: "My Message",
                      delegate: self,
                      cancelButtonTitle: "Cancel",
                      otherButtonTitles: "OK"
                    )
    

    By the way, this is the error I was getting (as of Xcode 6.4):

    Cannot find an initializer for type 'UIAlertView' that accepts an argument list of type '(title: String, message: String, delegate: MyViewController, cancelButtonTitle: String, otherButtonTitles: String)'

    As others mentioned, you should migrate to UIAlertController if you can target iOS 8.x+. To support iOS 7, use the code above (iOS 6 is not supported by Swift).

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  • lrony* 2015-09-17 13:48

    I have another trick. Suppose you have 5 classes where a logout alert to be applied. Try with swift class extension.

    File- New- Swift class- Name it.

    Add the following:

    public extension UIViewController
    {
    
        func makeLogOutAlert()
        {
            var refreshAlert = UIAlertController(title: "Log Out", message: "Are You Sure to Log Out ? ", preferredStyle: UIAlertControllerStyle.Alert)
    
            refreshAlert.addAction(UIAlertAction(title: "Confirm", style: .Default, handler: { (action: UIAlertAction!) in
                self.navigationController?.popToRootViewControllerAnimated(true)
            }))
    
            refreshAlert.addAction(UIAlertAction(title: "Cancel", style: .Default, handler: { (action: UIAlertAction!) in
                refreshAlert .dismissViewControllerAnimated(true, completion: nil)
            }))
    
            presentViewController(refreshAlert, animated: true, completion: nil)
        }
    }
    

    Implement using : self.makeLogOutAlert(). Hope it helps.

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  • Didn"t forge 2015-10-07 13:33

    With the protocol extensions of Swift 2, you can make a protocol that provides a default implementation to your view controllers:

    ShowsAlert.swift

    import UIKit
    
    protocol ShowsAlert {}
    
    extension ShowsAlert where Self: UIViewController {
        func showAlert(title: String = "Error", message: String) {
            let alertController = UIAlertController(title: title, message: message, preferredStyle: .Alert)
            alertController.addAction(UIAlertAction(title: "Ok", style: .Default, handler: nil))
            presentViewController(alertController, animated: true, completion: nil)
        }
    }
    

    ViewController.swift

    class ViewController: UIViewController, ShowsAlert {
        override func viewDidLoad() {
            super.viewDidLoad()
            showAlert(message: "Hey there, I am an error message!")
        }
    }
    
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  • 七度&光 2015-10-26 07:44

    One Button

    One Button Screenshot

    class ViewController: UIViewController {
    
        @IBAction func showAlertButtonTapped(_ sender: UIButton) {
    
            // create the alert
            let alert = UIAlertController(title: "My Title", message: "This is my message.", preferredStyle: UIAlertController.Style.alert)
    
            // add an action (button)
            alert.addAction(UIAlertAction(title: "OK", style: UIAlertAction.Style.default, handler: nil))
    
            // show the alert
            self.present(alert, animated: true, completion: nil)
        }
    }
    

    Two Buttons

    Two Button Alert Screenshot

    class ViewController: UIViewController {
    
        @IBAction func showAlertButtonTapped(_ sender: UIButton) {
    
            // create the alert
            let alert = UIAlertController(title: "UIAlertController", message: "Would you like to continue learning how to use iOS alerts?", preferredStyle: UIAlertController.Style.alert)
    
            // add the actions (buttons)
            alert.addAction(UIAlertAction(title: "Continue", style: UIAlertAction.Style.default, handler: nil))
            alert.addAction(UIAlertAction(title: "Cancel", style: UIAlertAction.Style.cancel, handler: nil))
    
            // show the alert
            self.present(alert, animated: true, completion: nil)
        }
    }
    

    Three Buttons

    enter image description here

    class ViewController: UIViewController {
    
        @IBAction func showAlertButtonTapped(_ sender: UIButton) {
    
            // create the alert
            let alert = UIAlertController(title: "Notice", message: "Lauching this missile will destroy the entire universe. Is this what you intended to do?", preferredStyle: UIAlertController.Style.alert)
    
            // add the actions (buttons)
            alert.addAction(UIAlertAction(title: "Remind Me Tomorrow", style: UIAlertAction.Style.default, handler: nil))
            alert.addAction(UIAlertAction(title: "Cancel", style: UIAlertActio.nStyle.cancel, handler: nil))
            alert.addAction(UIAlertAction(title: "Launch the Missile", style: UIAlertAction.Style.destructive, handler: nil))
    
            // show the alert
            self.present(alert, animated: true, completion: nil)
        }
    }
    

    Handling Button Taps

    The handler was nil in the above examples. You can replace nil with a closure to do something when the user taps a button. For example:

    alert.addAction(UIAlertAction(title: "Launch the Missile", style: UIAlertAction.Style.destructive, handler: { action in
    
        // do something like...
        self.launchMissile()
    
    }))
    

    Notes

    • Multiple buttons do not necessarily need to use different UIAlertAction.Style types. They could all be .default.
    • For more than three buttons consider using an Action Sheet. The setup is very similar. Here is an example.
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  • 程序go 2015-10-26 09:31

    I have made a singleton class to make this convenient to use from anywhere in your app: https://github.com/Swinny1989/Swift-Popups

    You can then create a popup with multiple buttons like this:

    Popups.SharedInstance.ShowAlert(self, title: "Title goes here", message: "Messages goes here", buttons: ["button one" , "button two"]) { (buttonPressed) -> Void in
        if buttonPressed == "button one" { 
          //Code here
        } else if buttonPressed == "button two" {
            // Code here
        }
    }
    

    or popups with a single button like this:

    Popups.SharedInstance.ShowPopup("Title goes here", message: "Message goes here.")
    
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  • 乱世@小熊 2016-06-15 09:04

    Here is a pretty simple function of AlertView in Swift :

    class func globalAlertYesNo(msg: String) {
            let alertView = UNAlertView(title: "Title", message: msg)
    
            alertView.messageAlignment = NSTextAlignment.Center
            alertView.buttonAlignment  = UNButtonAlignment.Horizontal
    
            alertView.addButton("Yes", action: {
    
                print("Yes action")
    
            })
    
            alertView.addButton("No", action: {
    
                print("No action")
    
            })
    
            alertView.show()
    
        }
    

    You have to pass message as a String where you use this function.

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  • Memor.の 2016-07-04 08:43

    The Old Way: UIAlertView

    let alertView = UIAlertView(title: "Default Style", message: "A standard alert.", delegate: self, cancelButtonTitle: "Cancel", otherButtonTitles: "OK")
    alertView.alertViewStyle = .Default
    alertView.show()
    
    // MARK: UIAlertViewDelegate
    
     func alertView(alertView: UIAlertView, clickedButtonAtIndex buttonIndex: Int) {
     switch buttonIndex {
    
        // ...
       }
      }
    

    The New Way: UIAlertController

    let alertController = UIAlertController(title: "Default Style", message: "A standard alert.", preferredStyle: .Alert)
    
    let cancelAction = UIAlertAction(title: "Cancel", style: .Cancel) { (action) in
    // ...
     }
     alertController.addAction(cancelAction)
    
     let OKAction = UIAlertAction(title: "OK", style: .Default) { (action) in
    // ...
     }
     alertController.addAction(OKAction)
     self.presentViewController(alertController, animated: true) {
     // ...
    }
    
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  • Memor.の 2016-09-28 12:52

    Swift 3

    The following is a simple example of how to create a simple alert with one button with Swift 3.

    let alert = UIAlertController(title: "Title",
                                  message: "Message",
                                  preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "Ok", style: .default))
    present(alert, animated: true)
    

    In the above example the handle callback of the action has been omitted because the default behaviour of an alert view with one button is to disappear when the button is clicked.

    Here is how to create another action, which could be added to the alert with "alert.addAction(action)". The different styles are .default, .destructive and .cancel.

    let action = UIAlertAction(title: "Ok", style: .default) { action in
        // Handle when button is clicked    
    }
    
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  • from.. 2016-10-10 02:47

    Use this code to display an alertview

      let alertController = UIAlertController(title: "Hello  Coders", message: "your alert message", preferredStyle: .Alert)
            let defaultAction = UIAlertAction(title: "Close Alert", style: .Default, handler: nil)
            alertController.addAction(defaultAction)
    
            presentViewController(alertController, animated: true, completion: nil)
    

    Reference: Swift Show Alert using UIAlertController

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  • 狐狸.fox 2017-10-05 06:34

    in xcode 9

    let alert = UIAlertController(title: "Alert", message: "message", preferredStyle: UIAlertControllerStyle.alert)
    alert.addAction(UIAlertAction(title: "Ok", style: UIAlertActionStyle.default, handler: nil))
    self.present(alert, animated: true, completion: nil)
    
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  • ?yb? 2017-12-01 08:00

    try This. Put Bellow Code In Button.

    let alert = UIAlertController(title: "Your_Title_Text", message: "Your_MSG", preferredStyle: UIAlertControllerStyle.alert)
    alert.addAction(UIAlertAction(title: "Your_Text", style: UIAlertActionStyle.default, handler: nil))
    self.present(alert, animated:true, completion: nil)
    
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  • YaoRaoLov 2017-12-28 10:46

    on IOS 9, you can do this

    let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: UIAlertControllerStyle.alert)
    alert.addAction(UIAlertAction(title: "Click", style: UIAlertActionStyle.default, handler: nil))
    self.present(alert, animated: true, completion: nil)
    
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  • 叼花硬汉 2018-01-20 15:04

    For SWIFT4, I think, extending UIViewController and creating a reusable confirmation control is the most elegant way.

    You can extend the UIViewController as below:

    extension UIViewController {
    
    func AskConfirmation (title:String, message:String, completion:@escaping (_ result:Bool) -> Void) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
        self.present(alert, animated: true, completion: nil)
    
        alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: { action in
            completion(true)
        }))
    
        alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: { action in
            completion(false)
        }))
      }
    }
    

    Then you can use it anytime:

     AskConfirmation(title: "YOUR MESSAGE TITLE", message: "YOUR MESSAGE") { (result) in
            if result { //User has clicked on Ok
    
            } else { //User has clicked on Cancel
    
            }
        }
    
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  • 7*4 2018-02-28 13:24

    // Generic Class For UIAlertView

    //MARK:- MODULES
    import Foundation
    import UIKit
    
    //MARK:- CLASS
    class Alert  : NSObject{
    
    static let shared = Alert()
    
    var okAction : AlertSuccess?
    typealias AlertSuccess = (()->())?
    var alert: UIAlertController?
    
    /** show */
    public func show(title : String?, message : String?, viewController : UIViewController?, okAction : AlertSuccess = nil) {
    
        let version : NSString = UIDevice.current.systemVersion as NSString
        if  version.doubleValue >= 8 {
            alert = UIAlertController(title: title, message: message, preferredStyle:.alert)
            alert?.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action: UIAlertAction) in
    
                if let okAction = okAction {
                    okAction()
                }
            }))
            viewController?.present(alert ?? UIAlertController(), animated:true, completion:nil);
        }
    }
    
    /** showWithCancelAndOk */
    public func showWithCancelAndOk(title : String, okTitle : String, cancelTitle : String, message : String, viewController : UIViewController?, okAction : AlertSuccess = nil, cancelAction : AlertSuccess = nil) {
        let version:NSString = UIDevice.current.systemVersion as NSString;
    
        if  version.doubleValue >= 8 {
            alert = UIAlertController(title: title, message: message, preferredStyle:.alert)
    
            alert?.addAction(UIAlertAction(title: cancelTitle, style: .default, handler: { (action: UIAlertAction) in
    
                if let cancelAction = cancelAction {
                    cancelAction()
                }
            }))
            alert?.addAction(UIAlertAction(title: okTitle, style: .default, handler: { (action: UIAlertAction) in
    
                if let okAction = okAction {
                    okAction()
                }
            }))
            viewController?.present(alert!, animated:true, completion:nil);
        }
    }
    
    /** showWithTimer */
    public func showWithTimer(message : String?, viewController : UIViewController?) {
    
        let version : NSString = UIDevice.current.systemVersion as NSString
        if  version.doubleValue >= 8 {
            alert = UIAlertController(title: "", message: message, preferredStyle:.alert)
            viewController?.present(alert ?? UIAlertController(), animated:true, completion:nil)
            let when = DispatchTime.now() + 1
            DispatchQueue.main.asyncAfter(deadline: when){
                self.alert?.dismiss(animated: true, completion: nil)
            }
        }
    }
    }
    

    Use:-

    Alert.shared.show(title: "No Internet Connection", message: "The internet connection appers to be offline.", viewController: self) //without ok action
    
    Alert.shared.show(title: "No Internet Connection", message: "The internet connection appers to be offline.", viewController: self, okAction: {
                                //ok action
                            }) // with ok action
    
    Alert.shared.show(title: "No Internet Connection", message: "The internet connection appers to be offline.", viewController: self, okAction: {
                                //ok action 
    }, cancelAction: {
     //cancel action
    }) //with cancel and ok action
    
    Alert.shared.showWithTimer(message : "This is an alert with timer", viewController : self) //with timer
    
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  • 笑故挽风 2018-03-08 09:28
     let alertController = UIAlertController(title: "Select Photo", message: "Select atleast one photo", preferredStyle: .alert)
        let action1 = UIAlertAction(title: "From Photo", style: .default) { (action) in
            print("Default is pressed.....")
        }
        let action2 = UIAlertAction(title: "Cancel", style: .cancel) { (action) in
            print("Cancel is pressed......")
        }
        let action3 = UIAlertAction(title: "Click new", style: .default) { (action) in
            print("Destructive is pressed....")
    
        }
        alertController.addAction(action1)
        alertController.addAction(action2)
        alertController.addAction(action3)
        self.present(alertController, animated: true, completion: nil)
    
    }
    
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  • 喵-见缝插针 2018-05-04 07:03
      // UIAlertView is deprecated. Use UIAlertController 
      // title = title of the alert view.
      // message = Alert message you want to show.
      // By tap on "OK" , Alert view will dismiss.
    
     UIAlertView(title: "Alert", message: "Enter Message here.", delegate: nil, cancelButtonTitle: "OK").show()
    
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  • Memor.の 2018-06-03 13:37

    SWIFT 4 : Simply create a extension to UIViewController as follows:

       extension  UIViewController{
    
       func showSucsessAlert(withTitle title: String, andMessage 
        message:String){
            let alert = UIAlertController(title: title, message: message, 
             preferredStyle: UIAlertControllerStyle.alert)
            alert.addAction(UIAlertAction(title: "OK", style: 
            UIAlertActionStyle.default, handler: nil))
            self.present(alert, animated: true, completion: nil)
             }
        }
    

    Now in your viewcontroller, directly call above function as if they are provided by UIViewController.

        yourViewController.showSucsessAlert(withTitle: 
          "YourTitle", andMessage: "YourCustomTitle")
    
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  • python小菜 2018-08-15 11:01

    Below is the reusable code for alert view and action sheet, Just write one line to show alert anywhere in application

    class AlertView{
    
        static func show(title:String? = nil,message:String?,preferredStyle: UIAlertControllerStyle = .alert,buttons:[String] = ["Ok"],completionHandler:@escaping (String)->Void){
            let alert = UIAlertController(title: title, message: message, preferredStyle: preferredStyle)
    
            for button in buttons{
    
                var style = UIAlertActionStyle.default
                let buttonText = button.lowercased().replacingOccurrences(of: " ", with: "")
                if buttonText == "cancel"{
                    style = .cancel
                }
                let action = UIAlertAction(title: button, style: style) { (_) in
                    completionHandler(button)
                }
                alert.addAction(action)
            }
    
            DispatchQueue.main.async {
                if let app = UIApplication.shared.delegate as? AppDelegate, let rootViewController = app.window?.rootViewController {
                    rootViewController.present(alert, animated: true, completion: nil)
                }
    
            }
        }
    }
    

    Usage :

    class ViewController: UIViewController {
    
        override func viewWillAppear(_ animated: Bool) {
            AlertView.show(title: "Alert", message: "Are you sure ?", preferredStyle: .alert, buttons: ["Yes","No"]) { (button) in
                print(button)
            }
        }
    
    }
    
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  • ?yb? 2018-08-16 12:17

    In Swift 4.1 and Xcode 9.4.1

    SIMPLE ALERT

    let alert = UIAlertController(title: ""Your title, message: "Your message", preferredStyle: .alert)
    
         let ok = UIAlertAction(title: "OK", style: .default, handler: { action in
         })
         alert.addAction(ok)
         let cancel = UIAlertAction(title: "Cancel", style: .default, handler: { action in
         })
         alert.addAction(cancel)
         DispatchQueue.main.async(execute: {
            self.present(alert, animated: true)
    })
    

    ALERT WITH SHARED CLASS

    If you want Shared class style(Write once use every where)

    import UIKit
    class SharedClass: NSObject {//This is shared class
    static let sharedInstance = SharedClass()
    
        //Show alert
        func alert(view: UIViewController, title: String, message: String) {
            let alert = UIAlertController(title: title, message: message, preferredStyle: .alert)
            let defaultAction = UIAlertAction(title: "OK", style: .default, handler: { action in
            })
            alert.addAction(defaultAction)
            DispatchQueue.main.async(execute: {
                view.present(alert, animated: true)
            })
        }
    
        private override init() {
        }
    }
    

    Now call alert like this in every ware

    SharedClass.SharedInstance.alert(view: self, title: "Your title here", message: "Your message here")
    

    PRESENT ALERT TOP ALL WINDOWS

    If you want to present alert on top of all views, use this code

    func alertWindow(title: String, message: String) {
        DispatchQueue.main.async(execute: {
            let alertWindow = UIWindow(frame: UIScreen.main.bounds)
            alertWindow.rootViewController = UIViewController()
            alertWindow.windowLevel = UIWindowLevelAlert + 1
    
            let alert2 = UIAlertController(title: title, message: message, preferredStyle: .alert)
            let defaultAction2 = UIAlertAction(title: "OK", style: .default, handler: { action in
            })
            alert2.addAction(defaultAction2)
    
            alertWindow.makeKeyAndVisible()
    
            alertWindow.rootViewController?.present(alert2, animated: true, completion: nil)
        })
    }
    

    Function calling

    SharedClass.sharedInstance.alertWindow(title:"This your title", message:"This is your message")
    

    ALERT WITH TEXTFIELDS

    If you want to add textfields to alert.

    //Global variables
    var name:String?
    var login:String?
    
    //Call this function like this:  alertWithTF() 
    //Add textfields to alert 
    func alertWithTF() {
    
        let alert = UIAlertController(title: "Login", message: "Enter username&password", preferredStyle: .alert)
        // Login button
        let loginAction = UIAlertAction(title: "Login", style: .default, handler: { (action) -> Void in
            // Get TextFields text
            let usernameTxt = alert.textFields![0]
            let passwordTxt = alert.textFields![1]
            //Asign textfileds text to our global varibles
            self.name = usernameTxt.text
            self.login = passwordTxt.text
    
            print("USERNAME: \(self.name!)\nPASSWORD: \(self.login!)")
        })
    
        // Cancel button
        let cancel = UIAlertAction(title: "Cancel", style: .destructive, handler: { (action) -> Void in })
    
        //1 textField for username
        alert.addTextField { (textField: UITextField) in
            textField.placeholder = "Enter username"
            //If required mention keyboard type, delegates, text sixe and font etc...
            //EX:
            textField.keyboardType = .default
        }
    
        //2nd textField for password
        alert.addTextField { (textField: UITextField) in
            textField.placeholder = "Enter password"
            textField.isSecureTextEntry = true
        }
    
        // Add actions
        alert.addAction(loginAction)
        alert.addAction(cancel)
        self.present(alert, animated: true, completion: nil)
    
    }
    
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