IOS create UIAlertViewController programmatically - ios

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?

Answer 1

- (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];
}

Answer 2

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?

Answer 3

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)

Answer 4

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>)
}
}