How to present UIAlertController when not in a view controller

Question

Scenario  The user taps on a button on a view controller  The view controller is the topmost  obviously  in the navigation stack  The tap invokes a utility class method called on another class  A bad thing happens there and I want to display an alert right there before control returns to the view controller      void myUtilityMethod          do stuff        something bad happened  display an alert      This was possible with UIAlertView  but perhaps not quite proper     In this case  how do you present a UIAlertController  right there in myUtilityMethod

User · Answer

Cross post my answer since these two threads are not flagged as dupes...

Now that UIViewController is part of the responder chain, you can do something like this:

if let vc = self.nextResponder()?.targetForAction(#selector(UIViewController.presentViewController(_:animated:completion:)), withSender: self) as? UIViewController {

    let alert = UIAlertController(title: "A snappy title", message: "Something bad happened", preferredStyle: .Alert)
    alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))

    vc.presentViewController(alert, animated: true, completion: nil)
}

User · Answer

There 2 approaches that you can use   -Use UIAlertView or  UIActionSheet  instead  not recommended  cause it deprecated in iOS 8 but it works now   -Somehow remember the last view controller which is presented  Here is example    interface UIViewController  TopController     UIViewController   topViewController   end     implementation   import  UIViewController TopController h   import  lt objc runtime h gt   static   weak UIViewController   topViewController   nil    implementation UIViewController  TopController      UIViewController   topViewController       UIViewController  vc    topViewController      while  vc parentViewController            vc   vc parentViewController            return vc        void load        super load        self swizzleSelector  selector viewDidAppear   withSelector  selector myViewDidAppear          self swizzleSelector  selector viewWillDisappear   withSelector  selector myViewWillDisappear        -  void myViewDidAppear  BOOL animated       if   topViewController    nil             topViewController   self              self myViewDidAppear animated      -  void myViewWillDisappear  BOOL animated       if   topViewController    self             topViewController   nil              self myViewWillDisappear animated         void swizzleSelector  SEL sel1 withSelector  SEL sel2       Class class    self class        Method originalMethod   class getInstanceMethod class  sel1       Method swizzledMethod   class getInstanceMethod class  sel2        BOOL didAddMethod   class addMethod class                                          sel1                                          method getImplementation swizzledMethod                                           method getTypeEncoding swizzledMethod         if  didAddMethod            class replaceMethod class                              sel2                              method getImplementation originalMethod                               method getTypeEncoding originalMethod          else           method exchangeImplementations originalMethod  swizzledMethod             end    Usage     UIViewController topViewController  presentViewController alertController

User · Answer

Here s mythicalcoder s answer as an extension  tested  amp  working in Swift 4   extension UIAlertController        func presentInOwnWindow animated  Bool  completion      - gt  Void              let alertWindow   UIWindow frame  UIScreen main bounds          alertWindow rootViewController   UIViewController           alertWindow windowLevel   UIWindowLevelAlert   1          alertWindow makeKeyAndVisible           alertWindow rootViewController  present self  animated  animated  completion  completion             Example usage   let alertController   UIAlertController title    lt Alert Title gt    message    lt Alert Message gt    preferredStyle   alert  alertController addAction UIAlertAction title   Close   style   cancel  handler  nil   alertController presentInOwnWindow animated  true  completion        print  completed

User · Answer

I use this code with some little personal variations in my AppDelegate class  - UIViewController  presentingRootViewController       UIViewController  vc   self window rootViewController      if   vc isKindOfClass  UINavigationController class               vc isKindOfClass  UITabBarController class                     filter nav controller         vc    AppDelegate findChildThatIsNotNavController vc              filter tab controller         if   vc isKindOfClass  UITabBarController class                  UITabBarController  tbc     UITabBarController  vc               if   tbc viewControllers  count  gt  0                    vc    tbc viewControllers  tbc selectedIndex                      filter nav controller again                 vc    AppDelegate findChildThatIsNotNavController vc                                     return vc             Private helper       UIViewController  findChildThatIsNotNavController  UIViewController  vc       if   vc isKindOfClass  UINavigationController class              if    UINavigationController   vc  viewControllers count  gt  0                vc      UINavigationController   vc  viewControllers objectAtIndex 0                       return vc

User · Answer

You can try to implement a category on UIViewController with mehtod like  -  void presentErrorMessage  And and inside that method you implement UIAlertController and then present it on self  Than in your client code you will have something like    myViewController presentErrorMessage    In that way you ll avoid unneccessary parametrs and warnings about view not being in window hierarchy

User · Answer

Updated to work with iOS 13 Scenes which breaks the new UIWindow approach  Swift 5 1   fileprivate var alertWindows    UIAlertController UIWindow     extension UIAlertController        func presentInNewWindow animated  Bool  completion      - gt  Void              let foregroundActiveScene   UIApplication shared connectedScenes filter    0 activationState     foregroundActive   first         guard let foregroundWindowScene   foregroundActiveScene as  UIWindowScene else   return            let window   UIWindow windowScene  foregroundWindowScene          alertWindows self    window          window rootViewController   UIViewController           window windowLevel    alert   1         window makeKeyAndVisible           window rootViewController  present  self  animated  animated  completion  completion             open override func viewDidDisappear   animated  Bool            super viewDidDisappear animated          alertWindows self    nil

User · Answer

If anyone is interested I created a Swift 3 version of  agilityvision answer  The code   import Foundation import UIKit  extension UIAlertController        var window  UIWindow            get               return objc getAssociatedObject self   window   as  UIWindow                   set               objc setAssociatedObject self   window   newValue  objc AssociationPolicy OBJC ASSOCIATION RETAIN NONATOMIC                       open override func viewDidDisappear   animated  Bool            super viewDidDisappear animated          self window  isHidden   true         self window   nil            func show animated  Bool   true            let window   UIWindow frame  UIScreen main bounds          window rootViewController   UIViewController nibName  nil  bundle  nil           let delegate   UIApplication shared delegate         if delegate  window    nil               window tintColor   delegate  window   tintColor                    window windowLevel   UIApplication shared windows last  windowLevel   1          window makeKeyAndVisible           window rootViewController  present self  animated  animated  completion  nil           self window   window

User · Answer

agilityvision s answer translated to Swift4 iOS11  I haven t used localized strings  but you can change that easily   import UIKit      An alert controller that can be called without a view controller   Creates a blank view controller and presents itself over that      class AlertPlusViewController  UIAlertController        private var alertWindow  UIWindow       override func viewDidLoad             super viewDidLoad              override func viewDidDisappear   animated  Bool            super viewDidDisappear animated          self alertWindow  isHidden   true         alertWindow   nil            func show             self showAnimated animated  true             func showAnimated animated    Bool             let blankViewController   UIViewController           blankViewController view backgroundColor   UIColor clear          let window   UIWindow frame  UIScreen main bounds          window rootViewController   blankViewController         window backgroundColor   UIColor clear         window windowLevel   UIWindowLevelAlert   1         window makeKeyAndVisible           self alertWindow   window          blankViewController present self  animated  true  completion  nil             func presentOkayAlertWithTitle title  String   message  String              let alertController   AlertPlusViewController title  title  message  message  preferredStyle   alert          let okayAction   UIAlertAction title   Ok   style   default  handler  nil          alertController addAction okayAction          alertController show              func presentOkayAlertWithError error  NSError             let title    Error          let message   error  localizedDescription         presentOkayAlertWithTitle title  title  message  message

User · Answer

Improving on agilityvision s answer  you ll need to create a window with a transparent root view controller and present the alert view from there   However as long as you have an action in your alert controller  you don t need to keep a reference to the window  As a final step of the action handler block  you just need to hide the window as part of the cleanup task  By having a reference to the window in the handler block  this creates a temporary circular reference that would be broken once the alert controller is dismissed   UIWindow  window     UIWindow alloc  initWithFrame  UIScreen mainScreen  bounds   window rootViewController    UIViewController new   window windowLevel   UIWindowLevelAlert   1   UIAlertController  alertCtrl    UIAlertController alertControllerWithTitle     message     preferredStyle UIAlertControllerStyleAlert     alertCtrl addAction  UIAlertAction actionWithTitle NSLocalizedString   OK    Generic confirm   style UIAlertActionStyleCancel handler   UIAlertAction    Nonnull action               do your stuff         very important to hide the window afterwards         this also keeps a reference to the window until the action is invoked      window hidden   YES         window makeKeyAndVisible    window rootViewController presentViewController alertCtrl animated YES completion nil

User · Answer

For iOS 13  building on the answers by mythicalcoder and bobbyrehm   In iOS 13  if you are creating your own window to present the alert in  you are required to hold a strong reference to that window or else your alert won t be displayed because the window will be immediately deallocated when its reference exits scope   Furthermore  you ll need to set the reference to nil again after the alert is dismissed in order to remove the window to continue to allow user interaction on the main window below it   You can create a UIViewController subclass to encapsulate the window memory management logic   class WindowAlertPresentationController  UIViewController           MARK  - Properties      private lazy var window  UIWindow    UIWindow frame  UIScreen main bounds      private let alert  UIAlertController         MARK  - Initialization      init alert  UIAlertController             self alert   alert         super init nibName  nil  bundle  nil             required init  coder aDecoder  NSCoder             fatalError  This initializer is not supported                 MARK  - Presentation      func present animated  Bool  completion      - gt  Void               window  rootViewController   self         window  windowLevel   UIWindow Level alert   1         window  makeKeyAndVisible           present alert  animated  animated  completion  completion                MARK  - Overrides      override func dismiss animated flag  Bool  completion      - gt  Void     nil             super dismiss animated  flag                self window   nil             completion                        You can use this as is  or if you want a convenience method on your UIAlertController  you can throw it in an extension   extension UIAlertController        func presentInOwnWindow animated  Bool  completion      - gt  Void               let windowAlertPresentationController   WindowAlertPresentationController alert  self          windowAlertPresentationController present animated  animated  completion  completion

User · Answer

create helper class AlertWindow and than use as  let alertWindow   AlertWindow    let alert   UIAlertController title   Hello   message   message   preferredStyle   alert   let cancel   UIAlertAction title   Ok   style   cancel   action  in              action code here         reference to alertWindow retain it  Every action must have this at end      alertWindow isHidden   true          here AlertWindow deinit        alert addAction cancel   alertWindow present alert  animated  true  completion  nil    class AlertWindow UIWindow       convenience init            self init frame UIScreen main bounds              override init frame  CGRect            super init frame  frame           if let color   UIApplication shared delegate  window   tintColor               tintColor   color                    rootViewController   UIViewController           windowLevel   UIWindowLevelAlert   1          makeKeyAndVisible              required init  coder aDecoder  NSCoder            fatalError  init coder   has not been implemented              deinit              semaphor signal               func present   ctrl UIViewController  animated Bool  completion     - gt Void             rootViewController  present ctrl  animated  animated  completion  completion

User · Answer

Swift 4   Solution I use for years with no issues at all  First of all I extend UIWindow to find it s visibleViewController  NOTE  if you using custom collection  classes  such as side menu  you should add handler for this case in following extension  After getting top most view controller it s easy to present UIAlertController just like UIAlertView   extension UIAlertController      func show animated  Bool   true  completion      - gt  Void     nil        if let visibleViewController   UIApplication shared keyWindow  visibleViewController         visibleViewController present self  animated  animated  completion  completion                extension UIWindow      var visibleViewController  UIViewController        guard let rootViewController   rootViewController else         return nil           return visibleViewController for  rootViewController         private func visibleViewController for controller  UIViewController  - gt  UIViewController       var nextOnStackViewController  UIViewController    nil     if let presented   controller presentedViewController         nextOnStackViewController   presented       else if let navigationController   controller as  UINavigationController        let visible   navigationController visibleViewController         nextOnStackViewController   visible       else if let tabBarController   controller as  UITabBarController        let visible    tabBarController selectedViewController            tabBarController presentedViewController          nextOnStackViewController   visible            if let nextOnStackViewController   nextOnStackViewController         return visibleViewController for  nextOnStackViewController        else         return controller

User · Answer

You can do the following with Swift 2 2   let alertController  UIAlertController       UIApplication sharedApplication   keyWindow  rootViewController  presentViewController alertController  animated  true  completion  nil    And Swift 3 0   let alertController  UIAlertController       UIApplication shared keyWindow  rootViewController  present alertController  animated  true  completion  nil

User · Answer

extension UIApplication           The top most view controller     static var topMostViewController  UIViewController            return UIApplication shared keyWindow  rootViewController  visibleViewController          extension UIViewController           The visible view controller from a given view controller     var visibleViewController  UIViewController            if let navigationController   self as  UINavigationController               return navigationController topViewController  visibleViewController           else if let tabBarController   self as  UITabBarController               return tabBarController selectedViewController  visibleViewController           else if let presentedViewController   presentedViewController               return presentedViewController visibleViewController           else               return self                     With this you can easily present your alert like so  UIApplication topMostViewController  present viewController  animated  true  completion  nil    One thing to note is that if there s a UIAlertController currently being displayed  UIApplication topMostViewController will return a UIAlertController  Presenting on top of a UIAlertController has weird behavior and should be avoided  As such  you should either manually check that   UIApplication topMostViewController is UIAlertController  before presenting  or add an else if case to return nil if self is UIAlertController  extension UIViewController           The visible view controller from a given view controller     var visibleViewController  UIViewController            if let navigationController   self as  UINavigationController               return navigationController topViewController  visibleViewController           else if let tabBarController   self as  UITabBarController               return tabBarController selectedViewController  visibleViewController           else if let presentedViewController   presentedViewController               return presentedViewController visibleViewController           else if self is UIAlertController               return nil           else               return self

User · Answer

Shorthand way to do present the alert in Objective-C       UIApplication sharedApplication  keyWindow  rootViewController  presentViewController alertController animated YES completion nil     Where alertController is your UIAlertController object   NOTE  You ll also need to make sure your helper class extends UIViewController

User · Answer

iOS13 scene support  when using UIWindowScene   import UIKit  private var windows   String UIWindow         extension UIWindowScene       static var focused  UIWindowScene            return UIApplication shared connectedScenes              first    0 activationState     foregroundActive  amp  amp   0 is UIWindowScene   as  UIWindowScene          class StyledAlertController  UIAlertController        var wid  String       func present animated  Bool  completion      - gt  Void                 let window   UIWindow frame  UIScreen main bounds          guard let window   UIWindowScene focused map UIWindow init windowScene    else               return                   window rootViewController   UIViewController           window windowLevel    alert   1         window makeKeyAndVisible           window rootViewController  present self  animated  animated  completion  completion           wid   UUID   uuidString         windows wid     window            open override func viewDidDisappear   animated  Bool            super viewDidDisappear animated          if let wid   wid               windows wid    nil

User · Answer

In Swift 3     let alertLogin   UIAlertController init title   Your Title   message  Your message   preferredStyle   alert                                      alertLogin addAction UIAlertAction title   Done   style  default  handler     AlertAction  in                                                                              self window  rootViewController  present alertLogin  animated  true  completion  nil

User · Answer

Seems to work   static UIViewController  viewControllerForView UIView  view        UIResponder  responder   view      do           responder    responder nextResponder             while  responder  amp  amp    responder isKindOfClass  UIViewController class         return  UIViewController   responder     - void showActionSheet       UIAlertController  alertController    UIAlertController alertControllerWithTitle nil message nil preferredStyle UIAlertControllerStyleActionSheet        alertController addAction  UIAlertAction actionWithTitle   Cancel  style UIAlertActionStyleCancel handler nil         alertController addAction  UIAlertAction actionWithTitle   Do it  style UIAlertActionStyleDefault handler nil         viewControllerForView self  presentViewController alertController animated YES completion nil

User · Answer

I tried everything mentioned  but with no success  The method which I used for Swift 3 0     extension UIAlertController       func show             present animated  true  completion  nil             func present animated  Bool  completion      - gt  Void              if var topController   UIApplication shared keyWindow  rootViewController               while let presentedViewController   topController presentedViewController                   topController   presentedViewController                           topController present self  animated  animated  completion  completion

User · Answer

Adding on to Zev s answer  and switching back to Objective-C   you could run into a situation where your root view controller is presenting some other VC via a segue or something else  Calling presentedViewController on the root VC will take care of this     UIApplication sharedApplication  keyWindow rootViewController presentedViewController presentViewController alertController animated YES completion         This straightened out an issue I had where the root VC had segued to another VC  and instead of presenting the alert controller  a warning like those reported above was issued   Warning  Attempt to present  lt UIAlertController  0x145bfa30 gt  on  lt UINavigationController  0x1458e450 gt  whose view is not in the window hierarchy    I haven t tested it  but this may also be necessary if your root VC happens to be a navigation controller

User · Answer

Some of these answers only worked partly for me  combining them in the following class method in AppDelegate was the solution for me  It works on iPad  in UITabBarController views  in UINavigationController  en when presenting modals  Tested on iOS 10 and 13      UIViewController   rootViewController       UIViewController  rootViewController    UIApplication sharedApplication  delegate window rootViewController      if  rootViewController isKindOfClass  UINavigationController class            rootViewController     UINavigationController   rootViewController  viewControllers firstObject      if  rootViewController isKindOfClass  UITabBarController class            rootViewController     UITabBarController   rootViewController  selectedViewController      if  rootViewController presentedViewController    nil          rootViewController   rootViewController presentedViewController      return rootViewController      Usage     AppDelegate rootViewController  presentViewController

User · Answer

Swift  let alertController   UIAlertController title   title   message   message   preferredStyle   alert        var rootViewController   UIApplication shared keyWindow  rootViewController if let navigationController   rootViewController as  UINavigationController       rootViewController   navigationController viewControllers first   if let tabBarController   rootViewController as  UITabBarController       rootViewController   tabBarController selectedViewController         rootViewController  present alertController  animated  true  completion  nil    Objective-C  UIAlertController  alertController    UIAlertController alertControllerWithTitle   Title  message   message  preferredStyle UIAlertControllerStyleAlert         id rootViewController    UIApplication sharedApplication  delegate window rootViewController  if  rootViewController isKindOfClass  UINavigationController class          rootViewController     UINavigationController   rootViewController  viewControllers firstObject    if  rootViewController isKindOfClass  UITabBarController class          rootViewController     UITabBarController   rootViewController  selectedViewController           rootViewController presentViewController alertController animated YES completion nil

User · Answer

At WWDC  I stopped in at one of the labs and asked an Apple Engineer this same question   quot What was the best practice for displaying a UIAlertController  quot  And he said they had been getting this question a lot and we joked that they should have had a session on it  He said that internally Apple is creating a UIWindow with a transparent UIViewController and then presenting the UIAlertController on it  Basically what is in Dylan Betterman s answer  But I didn t want to use a subclass of UIAlertController because that would require me changing my code throughout my app  So with the help of an associated object  I made a category on UIAlertController that provides a show method in Objective-C  Here is the relevant code   import  quot UIAlertController Window h quot   import  lt objc runtime h gt    interface UIAlertController  Window   -  void show  -  void show  BOOL animated    end   interface UIAlertController  Private    property  nonatomic  strong  UIWindow  alertWindow    end   implementation UIAlertController  Private    dynamic alertWindow   -  void setAlertWindow  UIWindow   alertWindow       objc setAssociatedObject self   selector alertWindow   alertWindow  OBJC ASSOCIATION RETAIN NONATOMIC      -  UIWindow   alertWindow       return objc getAssociatedObject self   selector alertWindow        end   implementation UIAlertController  Window   -  void show        self show YES      -  void show  BOOL animated       self alertWindow     UIWindow alloc  initWithFrame  UIScreen mainScreen  bounds       self alertWindow rootViewController     UIViewController alloc  init        id lt UIApplicationDelegate gt  delegate    UIApplication sharedApplication  delegate         Applications that does not load with UIMainStoryboardFile might not have a window property      if   delegate respondsToSelector  selector window                 we inherit the main window s tintColor         self alertWindow tintColor   delegate window tintColor                window level is above the top window  this makes the alert  if it s a sheet  show over the keyboard      UIWindow  topWindow    UIApplication sharedApplication  windows lastObject      self alertWindow windowLevel   topWindow windowLevel   1        self alertWindow makeKeyAndVisible        self alertWindow rootViewController presentViewController self animated animated completion nil      -  void viewDidDisappear  BOOL animated        super viewDidDisappear animated               precaution to ensure window gets destroyed     self alertWindow hidden   YES      self alertWindow   nil      end  Here is a sample usage     need local variable for TextField to prevent retain cycle of Alert otherwise UIWindow    would not disappear after the Alert was dismissed   block UITextField  localTextField  UIAlertController  alert    UIAlertController alertControllerWithTitle   quot Global Alert quot  message   quot Enter some text quot  preferredStyle UIAlertControllerStyleAlert    alert addAction  UIAlertAction actionWithTitle   quot OK quot  style UIAlertActionStyleDefault handler   UIAlertAction  action        NSLog   quot do something with text    quot   localTextField text      do NOT use alert textfields or otherwise reference the alert in the block  Will cause retain cycle       alert addTextFieldWithConfigurationHandler   UITextField  textField        localTextField   textField       alert show    The UIWindow that is created will be destroyed when the UIAlertController is dealloced  since it is the only object that is retaining the UIWindow  But if you assign the UIAlertController to a property or cause its retain count to increase by accessing the alert in one of the action blocks  the UIWindow will stay on screen  locking up your UI  See the sample usage code above to avoid in the case of needing to access UITextField  I made a GitHub repo with a test project  FFGlobalAlertController

User · Answer

Create Extension like in Aviel Gross answer  Here You have Objective-C extension   Here You have header file   h      UIAlertController Showable h   import  lt UIKit UIKit h gt    interface UIAlertController  Showable   -  void show   -  void presentAnimated  BOOL animated              completion  void     void  completion   -  void presentFromController  UIViewController   viewController                      animated  BOOL animated                    completion  void     void  completion    end   And implementation    m      UIAlertController Showable m   import  UIAlertController Showable h    implementation UIAlertController  Showable   -  void show        self presentAnimated YES completion nil      -  void presentAnimated  BOOL animated              completion  void     void  completion       UIViewController  rootVC    UIApplication sharedApplication  keyWindow rootViewController      if  rootVC    nil             self presentFromController rootVC animated animated completion completion            -  void presentFromController  UIViewController   viewController                      animated  BOOL animated                    completion  void     void  completion        if   viewController isKindOfClass  UINavigationController class              UIViewController  visibleVC     UINavigationController   viewController  visibleViewController           self presentFromController visibleVC animated animated completion completion         else if   viewController isKindOfClass  UITabBarController class              UIViewController  selectedVC     UITabBarController   viewController  selectedViewController           self presentFromController selectedVC animated animated completion completion         else            viewController presentViewController self animated animated completion completion             end   You are using this extension in Your implementation file like this    import  UIAlertController Showable h   UIAlertController  alert    UIAlertController     alertControllerWithTitle   Title here                       message   Detail message here                preferredStyle UIAlertControllerStyleAlert    UIAlertAction  defaultAction    UIAlertAction     actionWithTitle   OK                style UIAlertActionStyleDefault             handler   UIAlertAction   action        alert addAction defaultAction       Add more actions if needed   alert show

User · Answer

I posted a similar question a couple months ago and think I ve finally solved the problem  Follow the link at the bottom of my post if you just want to see the code   The solution is to use an additional UIWindow    When you want to display your UIAlertController    Make your window the key and visible window  window makeKeyAndVisible    Just use a plain UIViewController instance as the rootViewController of the new window   window rootViewController   UIViewController    Present your UIAlertController on your window s rootViewController   A couple things to note    Your UIWindow must be strongly referenced  If it s not strongly referenced it will never appear  because it is released   I recommend using a property  but I ve also had success with an associated object  To ensure that the window appears above everything else  including system UIAlertControllers   I set the windowLevel   window windowLevel   UIWindowLevelAlert   1    Lastly  I have a completed implementation if you just want to look at that   https   github com dbettermann DBAlertController

User · Answer

agilityvision s answer is so good  I have sense used in swift projects so  I thought I would share my take on his answer using swift 3 0  fileprivate class MyUIAlertController  UIAlertController      typealias Handler      - gt  Void    struct AssociatedKeys       static var alertWindowKey    alertWindowKey         dynamic var  alertWindow  UIWindow     var alertWindow  UIWindow        return objc getAssociatedObject self   amp AssociatedKeys alertWindowKey  as  UIWindow         func setAlert inWindow window  UIWindow        objc setAssociatedObject self   amp AssociatedKeys alertWindowKey   alertWindow   OBJC ASSOCIATION RETAIN NONATOMIC         func show completion  Handler    nil        show animated  true  completion  completion         func show animated  Bool  completion  Handler     nil         alertWindow   UIWindow frame  UIScreen main bounds       alertWindow  rootViewController   UIViewController        if let delegate  UIApplicationDelegate   UIApplication shared delegate  let window   delegate window          alertWindow  tintColor   window  tintColor             let topWindow   UIApplication shared windows last      alertWindow  windowLevel   topWindow  windowLevel    0   1      alertWindow  makeKeyAndVisible        alertWindow  rootViewController  present self  animated  animated  completion  completion         fileprivate override func viewDidDisappear   animated  Bool        super viewDidDisappear animated       alertWindow  isHidden   true      alertWindow   nil

User · Answer

You can send the current view or controller as a parameter      void myUtilityMethod  id controller          do stuff        something bad happened  display an alert

User · Answer

In addition to great answers given  agilityvision  adib  malhal   To reach queueing behaviour like in good old UIAlertViews  avoid alert windows overlap   use this block to observe window level availability    interface UIWindow  WLWindowLevel      void notifyWindowLevelIsAvailable  UIWindowLevel level withBlock  void       block    end   implementation UIWindow  WLWindowLevel      void notifyWindowLevelIsAvailable  UIWindowLevel level withBlock  void       block       UIWindow  keyWindow    UIApplication sharedApplication  keyWindow      if  keyWindow windowLevel    level               window level is occupied  listen for windows to hide         id observer          observer     NSNotificationCenter defaultCenter  addObserverForName UIWindowDidBecomeHiddenNotification object keyWindow queue nil usingBlock   NSNotification  note                  NSNotificationCenter defaultCenter  removeObserver observer                self notifyWindowLevelIsAvailable level withBlock block      recursive retry                    else           block       window level is available           end   Complete example    UIWindow notifyWindowLevelIsAvailable UIWindowLevelAlert withBlock        UIWindow  alertWindow     UIWindow alloc  initWithFrame  UIScreen mainScreen  bounds       alertWindow windowLevel   UIWindowLevelAlert      alertWindow rootViewController    UIViewController new        alertWindow makeKeyAndVisible        UIAlertController  alertController    UIAlertController alertControllerWithTitle   Alert  message nil preferredStyle UIAlertControllerStyleAlert        alertController addAction  UIAlertAction actionWithTitle   OK  style UIAlertActionStyleCancel handler   UIAlertAction  action            alertWindow hidden   YES                 alertWindow rootViewController presentViewController alertController animated YES completion nil         This will allow you to avoid alert windows overlap  Same method can be used to separate and put in queue view controllers for any number of window layers

User · Answer

This works in Swift for normal view controllers and even if there is a navigation controller on the screen   let alert   UIAlertController       let alertWindow   UIWindow frame  UIScreen main bounds  alertWindow rootViewController   UIViewController   alertWindow windowLevel   UIWindowLevelAlert   1  alertWindow makeKeyAndVisible   alertWindow rootViewController  presentViewController alert  animated  true  completion  nil

User · Answer

Pretty generic UIAlertController extension for all cases of UINavigationController and or UITabBarController  Also works if there s a modal VC on screen at the moment     Usage     option 1  myAlertController show     option 2  myAlertController present animated  true          completion code        This is the extension       Uses Swift1 2 syntax with the new if-let    so it won t compile on a lower version  extension UIAlertController        func show             present animated  true  completion  nil             func present  animated  Bool  completion      - gt  Void              if let rootVC   UIApplication sharedApplication   keyWindow  rootViewController               presentFromController rootVC  animated  animated  completion  completion                       private func presentFromController controller  UIViewController  animated  Bool  completion      - gt  Void              if  let navVC   controller as  UINavigationController              let visibleVC   navVC visibleViewController                   presentFromController visibleVC  animated  animated  completion  completion            else             if  let tabVC   controller as  UITabBarController                let selectedVC   tabVC selectedViewController                   presentFromController selectedVC  animated  animated  completion  completion              else                 controller presentViewController self  animated  animated  completion  completion

User · Answer

Register for a notification prior to calling the class method   Swift code   NSNotificationCenter defaultCenter   addObserver self  selector   displayAlert   name   ErrorOccured   object  nil    In the displayAlert instance method you could display your alert

User · Answer

Another option       var topController UIViewController   UIApplication shared keyWindow  rootViewController      while   topController presentedViewController     nil            topController   topController presentedViewController            topController present alert  animated true  completion nil

User · Answer

Kevin Sliech provided a great solution   I now use the below code in my main UIViewController subclass   One small alteration i made was to check to see if the best presentation controller is not a plain UIViewController  If not  it s got to be some VC that presents a plain VC  Thus we return the VC that s being presented instead   -  UIViewController   bestPresentationController       UIViewController  bestPresentationController    UIApplication sharedApplication  keyWindow rootViewController       if    bestPresentationController isMemberOfClass  UIViewController class                  bestPresentationController   bestPresentationController presentedViewController                 return bestPresentationController      Seems to all work out so far in my testing   Thank you Kevin

User · Answer

The following solution did not work even though it looked quite promising with all the versions  This solution is generating WARNING   Warning  Attempt to present  on  whose view is not in the window hierarchy   https   stackoverflow com a 34487871 2369867    This is looked promising then  But it was not in Swift 3  So I am answering this in Swift 3 and this is not template example    This is rather fully functional code by itself once you paste inside any function      Quick Swift 3 self-contained code   let alertController   UIAlertController title    lt your title gt    message    lt your message gt    preferredStyle  UIAlertControllerStyle alert  alertController addAction UIAlertAction title   Close   style  UIAlertActionStyle cancel  handler  nil    let alertWindow   UIWindow frame  UIScreen main bounds  alertWindow rootViewController   UIViewController   alertWindow windowLevel   UIWindowLevelAlert   1  alertWindow makeKeyAndVisible   alertWindow rootViewController  present alertController  animated  true  completion  nil    This is tested and working code in Swift 3

User · Answer

Swift 5 It s important to hide the window after showing the message  func showErrorMessage   message  String        let alertWindow   UIWindow frame  UIScreen main bounds      alertWindow rootViewController   UIViewController        let alertController   UIAlertController title   quot Error quot   message  message  preferredStyle  UIAlertController Style alert      alertController addAction UIAlertAction title   quot Close quot   style  UIAlertAction Style cancel  handler      in         alertWindow isHidden   true                  alertWindow windowLevel   UIWindow Level alert   1      alertWindow makeKeyAndVisible       alertWindow rootViewController  present alertController  animated  true  completion  nil

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Zev Eisenberg s answer is simple and straightforward  but it does not always work  and it may fail with this warning message    Warning  Attempt to present  lt UIAlertController  0x7fe6fd951e10 gt     on  lt ThisViewController  0x7fe6fb409480 gt  which is already presenting    lt AnotherViewController  0x7fe6fd109c00 gt    This is because the windows rootViewController is not at the top of the presented views  To correct this we need to walk up the presentation chain  as shown in my UIAlertController extension code written in Swift 3          show the alert in a view controller if specified  otherwise show from window s root pree func show inViewController  UIViewController         if let vc   inViewController           vc present self  animated  true  completion  nil        else              find the root  then walk up the chain         var viewController   UIApplication shared keyWindow  rootViewController         var presentedVC   viewController  presentedViewController         while presentedVC    nil               viewController   presentedVC             presentedVC   viewController  presentedViewController                      now we present         viewController  present self  animated  true  completion  nil           func show         show inViewController  nil      Updates on 9 15 2017   Tested and confirmed that the above logic still works great in the newly available iOS 11 GM seed  The top voted method by agilityvision  however  does not  the alert view presented in a newly minted UIWindow is below the keyboard and potentially prevents the user from tapping its buttons  This is because in iOS 11 all windowLevels higher than that of keyboard window is lowered to a level below it    One artifact of presenting from keyWindow though is the animation of keyboard sliding down when alert is presented  and sliding up again when alert is dismissed  If you want the keyboard to stay there during presentation  you can try to present from the top window itself  as shown in below code    func show inViewController  UIViewController         if let vc   inViewController           vc present self  animated  true  completion  nil        else              get a  solid  window with the highest level         let alertWindow   UIApplication shared windows filter    0 tintColor    nil     0 className       UIRemoteKeyboardWindow    sorted by     w1  w2  - gt  Bool in             return w1 windowLevel  lt  w2 windowLevel            last            save the top window s tint color         let savedTintColor   alertWindow  tintColor         alertWindow  tintColor   UIApplication shared keyWindow  tintColor             walk up the presentation tree         var viewController   alertWindow  rootViewController         while viewController  presentedViewController    nil               viewController   viewController  presentedViewController                    viewController  present self  animated  true  completion  nil             restore the top window s tint color         if let tintColor   savedTintColor               alertWindow  tintColor   tintColor                     The only not so great part of the above code is that it checks the class name UIRemoteKeyboardWindow to make sure we can include it too  Nevertheless the above code does work great in iOS 9  10 and 11 GM seed  with the right tint color and without the keyboard sliding artifacts

[ios] How to present UIAlertController when not in a view controller?

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