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, Aug 01 '16 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, Aug 01 '16 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 .' — Lê Khánh Vinh, Aug 01 '16 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, Aug 01 '16 at 15:45
are you testing with the simulator or with a real device and what is the ios version — caldera.sac, Aug 01 '16 at 15:50
I call the method by putting all the creation and call in viewdidappear. but can not call in viewdidload. i'm working with simulator ios 9.3 — Lê Khánh Vinh, Aug 01 '16 at 15:57
Have you put any breakpoints into your code to follow the execution path and make sure that what you think is happening is actually happening. — Abizern, Aug 01 '16 at 15:59
I thinks the problem is that can not call present view controller in viewdidload. If i put the call in other place everything working fine! — Lê Khánh Vinh, Aug 01 '16 at 16:01
Did you try checking out the new Documentation feature of Stackoverflow? This is extensively covered [here](http://stackoverflow.com/documentation/ios/874/uialertcontroller/2949/alert-views-with-uialertcontroller#t=201608020610222402166). — NSNoob, Aug 02 '16 at 06:10
https://stackoverflow.com/questions/24022479/how-would-i-create-a-uialertview-in-swift — Naresh, Sep 24 '19 at 05:08

score 72 · Accepted Answer · edited Sep 27 '17 at 21:06

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 '17 at 21:06

Graham

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answered Aug 01 '16 at 15:55

ChenSmile

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hi where to call the [self presentViewController:alert animated:YES completion:nil]; seem can not call in viewdidload – Lê Khánh Vinh Aug 01 '16 at 16:06
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 – Lê Khánh Vinh Aug 01 '16 at 16:08
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 – ChenSmile Aug 01 '16 at 16:09
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! – Lê Khánh Vinh Aug 01 '16 at 16:12
@LêKhánhVinh it is not good to have alert view controller in viewDidLoad. u can check after view get loaded – ChenSmile Aug 01 '16 at 16:13
Hi so where is good place to put it when user come to that viewcontroller? – Lê Khánh Vinh Aug 01 '16 at 16:18
@LêKhánhVinh check here ... http://stackoverflow.com/questions/26554894/how-to-present-uialertcontroller-when-not-in-a-view-controller – ChenSmile Aug 01 '16 at 16:22
Hi I found it only working good when we put in viewDidAppear. Everything seem working fine when move code to show UIalertViewController in viewDidAppear – Lê Khánh Vinh Aug 02 '16 at 01:46

score 7 · Answer 2 · edited Jun 11 '19 at 05:15

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?

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. — ja928, Jul 23 '20 at 21:48
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. — ghr, Aug 20 '22 at 05:35

score 2 · Answer 3 · edited May 17 '17 at 11:38

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 '17 at 11:38

carbonr

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answered Aug 01 '16 at 16:00

Ethan Parker

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1

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?) – Lê Khánh Vinh Aug 01 '16 at 16:20
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 – Ethan Parker Aug 01 '16 at 20:52
1

Hi i found put on view did load not working for alertViewController. Need to be in viewDidAppear – Lê Khánh Vinh Aug 02 '16 at 01:22
Nice catch, that will work or it should also work as an IBAction – Ethan Parker Aug 05 '16 at 18:03

Krunal · Answer 4 · 2018-04-18T09:40:39.987

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>)
    }
}

IOS create UIAlertViewController programmatically

4 Answers4

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