iOS - Alerts

Use of Alerts

Alerts are used to give important information 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

Now when we run the application we'll get the following output.