messagebox.m

- (IBAction)btnExit:(id)sender {
    UIAlertView *messageBox = [[UIAlertView alloc] initWithTitle:@"Exit"
                                                      message:@"Are you sure?"
                                                     delegate:self
                                            cancelButtonTitle:@"No"
                                            otherButtonTitles:@"Yes", nil];
    [messageBox show];
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    NSString *title = [alertView buttonTitleAtIndex:buttonIndex];
   
    if([title isEqualToString:@"No"]) {
        NSLog(@"No was selected.");
    }
    else if([title isEqualToString:@"Yes"]) {
        NSLog(@"Yes was selected.");
    }
}