- setKey:aKey The setKey: messages repositions the index to an entry having a key value that matches its argument. If there is more than one entry matching this key value, the index is positioned to the first entry that matches.
- getKey The getKey message returns the key value associated with the current location of the index. It returns nil if the index is not currently positioned at a member.
- next: (id *)key Return the next item and it's key.
- prev: (id *)key Return the previous item and it's key.
- get: (id *)key Return the current item and it's key.