Question

Each contact in the address book, has a unique Id,

1) will this Id ever change? if so when does it change? ie a user deletes a contact, will the other contact id change? how do we make sure of this? will not change now or in the future.

EDIT: would like to uniquely identify a contact, which id should I use as a reference?

Answer 1

The documentation says:

The recommended way to keep a
long-term reference to a particular
record is to store the first and last
name, or a hash of the first and last
name, in addition to the identifier.
When you look up a record by ID,
compare the record’s name to your
stored name. If they don’t match, use
the stored name to find the record,
and store the new ID for the record.