还有其他人在 Xcode 4.4 中收到此警告吗？
案例值不在枚举类型“MessageComposeResult”（又名“枚举 MessageComposeResult”）中
MFMailComposeResultFailed 包含在文档中关闭邮件撰写界面时返回的结果代码中。但是，文档列出了它，但 GCC 警告它不是 MessageComposeResult 中的枚举。为什么？
case MFMailComposeResultFailed:{
//do something here
}
break;
这是调用这种情况的扩展方法（我已将此枚举注释掉以禁用警告）：
- (void)messageComposeViewController:(MFMessageComposeViewController *)controller didFinishWithResult:(MessageComposeResult)result {
UIAlertView *errormsg = nil;
// Notifies users about errors associated with the interface
switch (result)
{
case MFMailComposeResultCancelled:
{
//Do something, If you need to
NSString *msgtitle = @"Cancelled Mail";
NSString *Bodymsg = @"Email Has been Cancelled by USER. You may continue to make modifications to the current attendance data at this point.";
errormsg = [[UIAlertView alloc] initWithTitle:msgtitle message:Bodymsg delegate:self cancelButtonTitle:@"Close" otherButtonTitles:nil];
}
break;
case MFMailComposeResultSaved:{/*Do nothing at this point*/}
break;
//NOTE: MFMailComposeResultFailed is included in Result codes returned when the mail composition interface is dismissed. However the documentation lists it but the GCC warns it is NOT an enum within MessageComposeResult. May be an Apple Bug.
/*case MFMailComposeResultFailed:{
NSString *title = @"Unable to Send Mail";
NSString *msg = @"Failed:\nmessage was not saved or queued, possibly due to an error.\nCheck your mail sent or draft items.";
errormsg = [[UIAlertView alloc] initWithTitle:title message:msg delegate:self cancelButtonTitle:@"Close" otherButtonTitles:nil];
}
break;
*/
case MFMailComposeResultSent:{
NSString *title = @"Mail Sent";
NSString *msg = @"Attendance Email has been sent. Thank you.";
errormsg = [[UIAlertView alloc] initWithTitle:title message:msg delegate:self cancelButtonTitle:@"Close" otherButtonTitles:nil];
//clean up data
//code here irrelevant
//set a completed flag for sent email in system
//display Alert and dismiss the mail composer view here
UIAlertView *alertView = nil;
if (result) {
alertView = [[UIAlertView alloc] initWithTitle:@"AttendanceViewController: viewDidLoad" message:@"updateProgressOfClassInstance FAILED" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
}
if (alertView != nil) {
[alertView show];
}
}
break;
default:
break;
}
//dismiss view and display any errors here.
[self dismissModalViewControllerAnimated:YES];
if (errormsg != nil) {
[errormsg show];
}
我希望这可以为你们澄清。谢谢！
（更新）好的，我的代码有几个我没有意识到的问题。我修复了它们，下面是正确的 switch 语句。
switch (result)
{
case MessageComposeResultCancelled:
{
//Do something, If you need to!
}
break;
case MessageComposeResultFailed:{
//Do something else, If you need to!!
}
break;
case MessageComposeResultSent:{
//Do something user friendly, If you need to!
}
break;
default:
break;
}
在自由世界和 stackoverflow 上继续摇滚！哇！