UIAlertController* alertController=[UIAlertController alertControllerWithTitle:@"您的選擇" message:[NSString stringWithFormat:@"%@",sender] preferredStyle:UIAlertControllerStyleAlert];

UIAlertAction* defaultAction=[UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {

}];//一個UIAlertAction 是UIAlertController的一個按鈕

[alertController addAction:defaultAction];

[self presentViewController:alertController animated:YES completion:nil];