gistfile1.txt

- (void)showSimpleAlert {

    UIAlertController *alertView = [UIAlertController alertControllerWithTitle:@"Alert!"
                                                                       message:@"This is an Alert."
                                                                preferredStyle:UIAlertControllerStyleAlert];
    
    [alertView addAction:[UIAlertAction actionWithTitle:@"ok"
                                                  style:UIAlertActionStyleDefault
                                                handler:^(UIAlertAction *action) {
                                                    NSLog(@"action - %@", action.title);
                                                }]];
    
    [self presentViewController:alertView animated:YES completion:^{
        NSLog(@"alertView shown!");
    }];
}

create a simple Alert.