ios – 在Obj-C中使用Switch语句

下面是一个Switch / Case语句,当无法发送电子邮件时显示错误消息.在大多数情况下,一切似乎都是正确的,但是当我将UIAlertView放入Switch语句时,我在 Xcode中收到错误：

switch (result) {
    case MFMailComposeResultCancelled:
        NSLog(@"Result: Mail sending canceled");
        break;
    case MFMailComposeResultFailed:
        NSLog(@"Result: Mail sending Failed");
        UIAlertView *message = [[UIAlertView alloc] initWithTitle:@"Sending Failed"
                                                          message:@"The email Could not be sent."
                                                         delegate:nil
                                                cancelButtonTitle:@"OK"
                                                otherButtonTitles:nil];

        [message show];
        break;
    default:
        NSLog(@"Result: Mail not sent");
        break;
}

为什么在将代码放入案例时会产生错误？

解决方法

把它放在括号中：

case MFMailComposeResultFailed: {
    NSLog(@"Result: Mail sending Failed");
    UIAlertView *message = [[UIAlertView alloc] initWithTitle:@"Sending Failed"
                                                      message:@"The email Could not be sent."
                                                     delegate:nil
                                            cancelButtonTitle:@"OK"
                                            otherButtonTitles:nil];

    [message show];
    break;
  }