On 2012-09-27 04:47:04 +0000, James Cameron said: > The only thing I don't quite understand is how sp_table is used > without triggering an error "UnboundLocalError: local variable > 'sp_table' referenced before assignment", but it works. Similar issue in obj-c and the logical you presented here. Conceptually I understand what's going on but implementation in obj-c is something I'm struggling with. Protocols, composites, containers, inheritance, no abstract classes, lots of learning. -- Bob Tanner <basic at us.netrek.org> Key fingerprint = 9906 320A 8BB6 64AD 96A7 7785 CBFB 10BF 568B F98C