IOS create UIAlertViewController programmatically

Question

I'm working on a ViewController with code (no storyboard). I'm trying to add and AlertController

I have declare propery in .m

@property (nonatomic, strong) UIAlertController *alertController;

And init in loadview method

//alertviewController
    _alertController = [[UIAlertController alloc]initWithNibName:nil bundle:nil];

And call the alertview in viewDidLoad:

_alertController = [UIAlertController alertControllerWithTitle:@"Error display content" message:@"Error connecting to server, no local database" preferredStyle:UIAlertControllerStyleAlert];

UIAlertAction *ok = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
                LandingPageViewController *viewController = [[LandingPageViewController alloc] initWithNibName:nil bundle:nil];
    //            viewController.showNavBarBackButton = YES;
                [[AppDelegate sharedAppDelegate].rootViewController cPushViewController:viewController];
}];
[_alertController addAction:ok];
[self presentViewController:_alertController animated:YES completion:nil];

I dont' know why the alert is not showing up. Some thing wrong with my code. How to set up and call alertViewController programmatically?

Hi tried but there is error no visible interface for 'UIAlertController' declares the selector 'show'. [_alertController show]; — Lê Khánh Vinh
– Lê Khánh Vinh, Commented Aug 1, 2016 at 15:16
Remove this line _alertController = [[UIAlertController alloc]initWithNibName:nil bundle:nil]; I'm not sure if that will fix the problem, but it's not needed, especially not in loadView, (did you mean viewDidLoad?) — James P
– James P, Commented Aug 1, 2016 at 15:18
Hi i put the calling code in viewdidAppear the alert show up but crash with this error: Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Application tried to present modally an active controller <StampCollectiblesMainViewController: 0x7b58d110>.' — Lê Khánh Vinh
– Lê Khánh Vinh, Commented Aug 1, 2016 at 15:25
it probably crashes on the button tap. which means make sure the alert dismisses and then the push takes place. call the push after delay — Shubhank
– Shubhank, Commented Aug 1, 2016 at 15:45

Graham · Accepted Answer · 2017-09-27 21:06:44Z

72

- (void)logoutButtonPressed
{
     UIAlertController * alert = [UIAlertController
                                 alertControllerWithTitle:@"Logout"
                                 message:@"Are You Sure Want to Logout!"
                                 preferredStyle:UIAlertControllerStyleAlert];

    //Add Buttons

    UIAlertAction* yesButton = [UIAlertAction
                                actionWithTitle:@"Yes"
                                style:UIAlertActionStyleDefault
                                handler:^(UIAlertAction * action) {
                                    //Handle your yes please button action here
                                    [self clearAllData];
                                }];

    UIAlertAction* noButton = [UIAlertAction
                               actionWithTitle:@"Cancel"
                               style:UIAlertActionStyleDefault
                               handler:^(UIAlertAction * action) {
                                   //Handle no, thanks button
                               }];

    //Add your buttons to alert controller

    [alert addAction:yesButton];
    [alert addAction:noButton];

    [self presentViewController:alert animated:YES completion:nil];
}

edited Sep 27, 2017 at 21:06

Graham

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answered Aug 1, 2016 at 15:55

ChenSmile

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8 Comments

Lê Khánh Vinh Over a year ago

hi where to call the [self presentViewController:alert animated:YES completion:nil]; seem can not call in viewdidload

Lê Khánh Vinh Over a year ago

Hi it working when i create separate method and call in viewdidload but there a warning in console: Presenting view controllers on detached view controllers is discouraged

ChenSmile Over a year ago

where r u performing ur alert controller, it may be button click or on some method, use above complete code in one method and call it in ur desire place. hope u got it

Lê Khánh Vinh Over a year ago

Hi my purpose is when user come to the viewcontroller the app will check whether coredata has record or not. if not and there is no internet connection . the app will show an error "no databae no internet connection" and move to home page!

ChenSmile Over a year ago

@LêKhánhVinh it is not good to have alert view controller in viewDidLoad. u can check after view get loaded

|

Deepzz · Accepted Answer · 2019-06-11 05:15:57Z

7

In Xcode 9.4.1

Create alert function globally and use every where.

//Alert function
- (void) showAlertMsg:(UIViewController *)viewController title:(NSString *)title message:(NSString *)message {

    UIAlertController * alert = [UIAlertController alertControllerWithTitle : title
                                                                    message : message
                                                             preferredStyle : UIAlertControllerStyleAlert];

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

    [alert addAction:ok];
    dispatch_async(dispatch_get_main_queue(), ^{
        [viewController presentViewController:alert animated:YES completion:nil];
    });

}

Call like this in your required place.

Import that class and create instance

//Ex:
GlobalClassViewController *gcvc = [[GlobalClassViewController alloc]init];

//Call alert function with instance
[gcvc showAlertMsg:self title:@"" message:placeholderText];

How would I create a UIAlertView in Swift?

edited Jun 11, 2019 at 5:15

Deepzz

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answered Aug 17, 2018 at 13:45

Naresh

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2 Comments

ja928 Over a year ago

The dispatch_async helped me get past some issues where my alerts weren't appearing because they were inadvertently created on view which were going out of scope.

ghr Over a year ago

The dispatch_async is necessary in iOS13+ with UISplitViewController on iPad (no scenes, no Storyboards). It is not required in iOS12 and lower. UI just locks up without showing the alert otherwise.

carbonr · Accepted Answer · 2017-05-17 11:38:48Z

2

And in Swift >=3:

  let alertController = UIAlertController(title: "Some Error",
                                               message: "Pleas confirm?",
                                               preferredStyle: .alert)

  let defaultAction = UIAlertAction(title: "OK", style: .default, handler: nil)
            alertController.addAction(defaultAction)

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

edited May 17, 2017 at 11:38

carbonr

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answered Aug 1, 2016 at 16:00

Ethan Parker

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4 Comments

Lê Khánh Vinh Over a year ago

hi so where is the place to place the code whenever user come to that viewcontroller and app has finished checked for some logic (for example no coredata to show?)

Ethan Parker Over a year ago

It's up to you, you can put it in viewDidLoad if you'd like it to be displayed when the user comes to that view or you can have it fired on a certain button press via IBAction

Lê Khánh Vinh Over a year ago

Hi i found put on view did load not working for alertViewController. Need to be in viewDidAppear

Ethan Parker Over a year ago

Nice catch, that will work or it should also work as an IBAction

Krunal · Accepted Answer · 2018-04-18 09:40:39Z

Create global Alert controller that is accessible in all view controllers using extension.
Create an extension of UIViewController with your function to display alert with required parameter arguments.

extension UIViewController {

      func displayalert(title:String, message:String) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
        alert.addAction((UIAlertAction(title: "OK", style: .default, handler: { (action) -> Void in

            alert.dismiss(animated: true, completion: nil)

        })))

        self.present(alert, animated: true, completion: nil)


      }
}

Now call this function from your view controller:

class TestViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        self.displayalert(title: <String>, message: <String>)
    }
}

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