The unique identifier in iOS App.

"UDID" is replaced in ios 7 with "identifierForVendor"!

Sometimes in our app we need the unique key for identifying the device or user.

We can use UDID till iOS 6 and identifierForVendor for iOS 7 onwards.

NSString *deviceUniqueId = [Self uniqueIDForDevice];

-(NSString*)uniqueIDForDevice

{

    NSString* uniqueIdentifier = nil;

    if( [UIDevice instancesRespondToSelector:@selector(identifierForVendor)] )

    {

        // >=iOS 7

        uniqueIdentifier = [[[UIDevice currentDevice] identifierForVendor] UUIDString];

    }

    else

    {  //<=iOS6, Use UDID of Device

        CFUUIDRef uuid = CFUUIDCreate(NULL);

        //uniqueIdentifier = ( NSString*)CFUUIDCreateString(NULL, uuid);- for non- ARC

        uniqueIdentifier = ( NSString*)CFBridgingRelease(CFUUIDCreateString(NULL, uuid));// for ARC

        CFRelease(uuid);

    }

    

    return uniqueIdentifier;

}

Important Note ---

UDID and identifierForVendor are different:---

1.) On uninstalling  and reinstalling the app identifierForVendor will change.

 2.) The value of identifierForVendor remains the same for all the apps installed from the same vendor on the device.

3.) The value of identifierForVendor also changes for all the apps if any of the app (from same vendor) is reinstalled.