enum in stringWithFormat provokes incompatible pointer type warning

Question

I have an enum property:

typedef enum syncCodeTypes {
    kCodeNull, 
    kCodeFoo,
    kCodeBar,
    kCodeDone
} syncCodeType;

//...

@property syncCodeType syncCode;

I use it in a stringWithFormat::

[self showAlertWithMessage:NSLocalizedString(@"Sync Error", @"Sync Error") andInfo:[NSString stringWithFormat:NSLocalizedString("Heads up re foobar code %d.", "Heads up re foobar code %d."), self.syncCode]];

…and get this warning:

Passing argument 1 of localizedStringForKey:value:table from incompatible pointer type.

Same thing happens if I substitue the unsigned conversion specifier (%u instead of %d). The compiler doesn’t like %lu, %ld, %llu, or %lld either.

Other posts regarding a related language advise that enums are neither signed nor unsigned, so I tried explicitly casting the enum to a signed and to an unsigned integer — and got exactly the same error message:

NSInteger iSyncCode = self.syncCode;
[self showAlertWithMessage:NSLocalizedString(@"Sync Error", @"Sync Error") andInfo:[NSString stringWithFormat:NSLocalizedString(“Heads up re foobar code %d.", “Heads up re foobar code %d."), iSyncCode]];
// compiler still annoyed

NSUInteger uSyncCode = self.syncCode;
[self showAlertWithMessage:NSLocalizedString(@"Sync Error", @"Sync Error") andInfo:[NSString stringWithFormat:NSLocalizedString(“Heads up re foobar code %u.”, “Heads up re foobar code %u.”), uSyncCode]];
// compiler still annoyed

In runtime there’s no problem — for now. But I'd like to be kosher. Any suggestions?

Answer 1

You forgot the @-sign before the strings in NSLocalizedString.

Replace "Heads up re foobar code %d." with @"Heads up re foobar code %d.".

Answer 2

The %d format specifier is for int variables. But self.syncCode is not an int, it is an syncCodeType.

You need to cast the value to an int:

(int)self.syncCode

or the whole line:

[self showAlertWithMessage:NSLocalizedString(@"Sync Error", @"Sync Error") andInfo:[NSString stringWithFormat:NSLocalizedString(@"Heads up re foobar code %d.", @"Heads up re foobar code %d."), (int)self.syncCode]];

This will make the compiler happy.

P.S. And as phix23 points out, you need to pass NSString literals, not C-string literals to NSLocalizedString.