actionscript 3 - JSON.decode issue -

i found old mmo game had been working on friend years ago, when running bellow code (from bigger file) keeps throwing:

roommanager.as(43): col: 14 error: access of undefined property json.

public function roommanager(_con:connection, _rmap:string = null, _rwarps:string = null)     {         _connection = _con;         roommap = json.decode (_rmap) array;         if(_rwarps != null && _rwarps != "") roomwarps = json.decode (_rwarps) array;         objectmanager.connection = _con;     } 

i have been unable find give me detail further explore issue, can advise at?

thanks