gistfile1.m

static NSString * const kKeyHasAttributedReferral = @"hasAttributedReferral";

- (void)attributeReferral {
  if([[NSUserDefaults standardUserDefaults] boolForKey:kKeyHasAttributedReferral]) {
    return;
  }
  // Attribute referrals
  NSMutableDictionary *params = [NSMutableDictionary dictionary];
  params[@"device"] = [[UIDevice currentDevice].model componentsSeparatedByString:@" "].firstObject;
  params[@"os_version"] = [[UIDevice currentDevice].systemVersion stringByReplacingOccurrencesOfString:@"." withString:@"_"];
  
  // Add any user-specific parameters and send it to the attribution script...
}