iOS - Alerts

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Use of Alerts

Alerts are used to give important informations to user. Only after selecting the option in the alert view, we can proceed further using the app.

Important Properties

• alertViewStyle
• cancelButtonIndex
• delegate
• message
• numberOfButtons
• title

Important Methods

- (NSInteger)addButtonWithTitle:(NSString *)title
- (NSString *)buttonTitleAtIndex:(NSInteger)buttonIndex
- (void)dismissWithClickedButtonIndex:
(NSInteger)buttonIndex animated:(BOOL)animated
- (id)initWithTitle:(NSString *)title message:
(NSString *)message delegate:(id)delegate
cancelButtonTitle:(NSString *)cancelButtonTitle
otherButtonTitles:(NSString*)otherButtonTitles, ...
- (void)show

Update ViewController.h as follows −

Make your class conform to alert view delegate protocol by adding < UIAlertViewDelegate> as shown below in ViewController.h.

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController<UIAlertViewDelegate>{
    
}
@end

Add Custom Method addAlertView

-(void)addAlertView{
    UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:
    @"Title" message:@"This is a test alert" delegate:self 
    cancelButtonTitle:@"Cancel" otherButtonTitles:@"Ok", nil];
    [alertView show];
}

Implement Alert View Delegate Method

#pragma mark - Alert view delegate
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:
  (NSInteger)buttonIndex{
    switch (buttonIndex) {
        case 0:
            NSLog(@"Cancel button clicked");
            break;
        case 1:
            NSLog(@"OK button clicked");
            break;
        
        default:
            break;
    }
}

Update viewDidLoad in ViewController.m as follows −

(void)viewDidLoad
{
   [super viewDidLoad];
   [self addAlertView];
}

Output

When we run the application, we'll get the following output −

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