You should store three values: the record ID, the first name, and the last name.
1) In the case that the record ID hasn't changed, you're golden - just use that to locate the proper record.
2) If ABAddressBookGetPersonWithRecordID()
does not locate a record for your stored record ID (it returns NULL), then you'll need to search the person records for a match based on the first and last name. You can drop down to using ABAddressBookCopyPeopleWithName()
potentially or write your own locating code if you already have an array with all the person records in-memory. Locating the new record is up to you. Once to locate the new record, you can update your data storage with the new record ID.
Ultimately, you end up storing the record ID to use directly incase it doesn't change (if you're lucky) plus storing some keys from the address book entry that are unlikely to change. The name of the person or organization associated with an address book entry is most likely to change. You should, of course, account for the case where you may not find a record with the stored record ID or by searching for the name. This could trivially mean that the record was deleted, or it could mean that the record was renamed. You should handle that case whichever way you decide is best for your specific application.