iOS: dispatch_get_global_queue QOS_CLASS_BACKGROUND crashes on 7.1.2

Question

I have following snippets of code that fetches contacts by using block:

if (&ABAddressBookCreateWithOptions != NULL) {
            CFErrorRef error = nil;

          


        

Answer 1

The QOS_CLASS_ identifiers were introduced in iOS 8. You need to use the DISPATCH_QUEUE_PRIORITY_ identifiers if you want to support iOS 7.