Dealing with duplicate contacts due to linked cards in iOS’ Address Book API

One method would be to only retrieve the contacts from the default address book source:

ABAddressBookRef addressBook = ABAddressBookCreate();
NSArray *people = (__bridge NSArray *)ABAddressBookCopyArrayOfAllPeopleInSource(addressBook, ABAddressBookCopyDefaultSource(addressBook));

But that is lame, right? It targets the on-device address book, but not extra contacts that might be in Exchange or other fancy syncing address books.

So here’s the solution you’re looking for:

1. Iterate through the ABRecord references
2. Grab each respective “linked references” (using ABPersonCopyArrayOfAllLinkedPeople)
3. Bundle them in an NSSet (so that the grouping can be uniquely identified)
4. Add that NSSet to another NSSet
5. Profit?

You now have an NSSet containing NSSets of linked ABRecord objects. The overarching NSSet will have the same count as the number of contacts in your “Contacts” app.

Example code:

NSMutableSet *unifiedRecordsSet = [NSMutableSet set];

ABAddressBookRef addressBook = ABAddressBookCreate();
CFArrayRef records = ABAddressBookCopyArrayOfAllPeople(addressBook);
for (CFIndex i = 0; i < CFArrayGetCount(records); i++)
{
    NSMutableSet *contactSet = [NSMutableSet set];

    ABRecordRef record = CFArrayGetValueAtIndex(records, i);
    [contactSet addObject:(__bridge id)record];

    NSArray *linkedRecordsArray = (__bridge NSArray *)ABPersonCopyArrayOfAllLinkedPeople(record);
    [contactSet addObjectsFromArray:linkedRecordsArray];

    // Your own custom "unified record" class (or just an NSSet!)
    DAUnifiedRecord *unifiedRecord = [[DAUnifiedRecord alloc] initWithRecords:contactSet];

    [unifiedRecordsSet addObject:unifiedRecord];
    CFRelease(record);
}

CFRelease(records);
CFRelease(addressBook);

_unifiedRecords = [unifiedRecordsSet allObjects];