identifierForVendor and iOS6

Question

The identifierForVendor require iOS6, so if my app currently supporting iOS4 and therefore I can't use it since my updates should always meet my app's previous min. requirement?

Answer 1

You can use this:

NSString *udid;

if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"6.0"))
    udid = [UIDevice currentDevice].identifierForVendor.UUIDString;
else
    udid = [UIDevice currentDevice].uniqueIdentifier;

with pre processor code:

#define SYSTEM_VERSION_EQUAL_TO(v)                  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedSame)
#define SYSTEM_VERSION_GREATER_THAN(v)              ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedDescending)
#define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN(v)                 ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(v)     ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedDescending)

Answer 2

You don't need preprocessor macros for this, you should check if it response, like this:

if ([[UIDevice currentDevice]respondsToSelector:@selector(identifierForVendor)]) {
    return [UIDevice currentDevice].identifierForVendor.UUIDString;
}else{
    // return [UIDevice currentDevice]. uniqueIdentifier
    return [[UIDevice currentDevice] performSelector:@selector(uniqueIdentifier)];
}