ABAddressBookRef addressBook = ABAddressBookCreate();
CFArrayRef people = ABAddressBookCopyArrayOfAllPeople(addressBook);
CFMutableArrayRef peopleMutable = CFArrayCreateMutableCopy(
														   kCFAllocatorDefault,
														   CFArrayGetCount(people),
														   people
														   );

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(%@ like %@)", kABPersonFirstNameProperty, aVariable];