Determine iPhone user's country

I need to determine at startup what country a user is in, for an iPhone application. Presumably I will have to turn on location services and do some sort of reverse geocoding. I don't really want to use a third party web service if possible, are there any other suggestions for determining country from what location services provides?

Initially, I only need to check whether the user is inside the US or not, but this may change in the future to add more countries. I understand that loca开发者_如何转开发tion can not always be determined or the user may have location services turned off. Basically, I just need to know if the user is detected as being inside the US, in order to turn off a specific feature.

EDIT: On further reading, it looks like MKReverseGeocoder would be the way to go, except I don't wish to display any maps in my app, which means I'm not allowed to use this.

Another trick you can try is checking the carrier’s MCC:

#import <CoreTelephony/CTTelephonyNetworkInfo.h>
#import <CoreTelephony/CTCarrier.h>

CTTelephonyNetworkInfo *netInfo = [[CTTelephonyNetworkInfo alloc] init];
CTCarrier *carrier = [netInfo subscriberCellularProvider];
NSString *mcc = [carrier mobileCountryCode];

NSLocale *locale = [NSLocale currentLocale];
NSString *countryCode = [locale objectForKey: NSLocaleCountryCode];

NSString *countryName = [locale displayNameForKey: NSLocaleCountryCode
                         value: countryCode];

Given the restrictions of MKReverseGeocoder, it seems the only feasible way for me to achieve what I am after is to use a third party service to perform a reverse geocode. I have chosen to go with GeoNames as they seem to be the standard choice.

The NSLocale object, such as returned by [NSLocale systemLocale], and[NSLocale autoupdatingCurrentLocale]`) contains the value NSLocaleCountryCode. Check it out in the Apple documentation.

If you don't want to use the Google services provided by the iPhone SDK, couldn't you just store the coordinates of the US of A borders and check whether or not you are inside that?

Here is a relevant question in that case How can I determine whether a 2D Point is within a Polygon?

If the purpose of the limitation is something other than user experience (for example, to enforce complicance with some specific US law), i.e. when the user can not be trused, I would say that you need some more rigorous checking (after all, the user would simply disallow the use of location services otherwise, wouldn't he/she?).

One such approach would be to do an IP lookup, e.g. http://www.maxmind.com/app/geoip_country