Determine iPhone user's country

问题:

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 location 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.

回答1:

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];

回答2:

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

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

回答3:

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.

回答4:

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

回答5:

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