iOS - Alerts

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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.

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