UIAlertController alert message

*.m

UIAlertController* alert = [UIAlertController alertControllerWithTitle:@"My Alert"
                                                                   message:@"This is an alert."
                                                          preferredStyle:UIAlertControllerStyleAlert];
    
UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault
                                                          handler:^(UIAlertAction * action) {
                                                              NSLog(@"this is my action");
                                                          }];
    
    [alert addAction:defaultAction];
    [self presentViewController:alert animated:YES completion:nil];