Is there any way to determine if the iphone is roaming?

Question

I am working on an iPhone application and would really like to determine if the device is roaming so that I can intelligently avoid costing my users expensive connections if

Answer 1

There is! It's not documented at all, and I highly doubt this would work on a non-jailbroken phone (as it requires using files not in the sandbox). However, here is how it is done.

The iPhone file system keeps two softlinks:

static NSString *carrierPListSymLinkPath = @"/var/mobile/Library/Preferences/com.apple.carrier.plist";
static NSString *operatorPListSymLinkPath = @"/var/mobile/Library/Preferences/com.apple.operator.plist";

when these links are pointing at the same file, the telephone is not roaming. When pointing at different files, the telephone is romaing.

Simplified code (no error checking, etc):

- (BOOL)isRoaming
{
    NSFileManager *fm = [NSFileManager defaultManager];
    NSError *error;
    NSString *carrierPListPath = [fm destinationOfSymbolicLinkAtPath:carrierPListSymLinkPath error:&error];
    NSString *operatorPListPath = [fm destinationOfSymbolicLinkAtPath:operatorPListSymLinkPath error:&error];
    return (![operatorPListPath isEqualToString:carrierPListPath]);
}