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 −