- create node_types table

[plcapi.git] / PLC / Table.py

diff --git a/PLC/Table.py b/PLC/Table.py
index fb19176..f37f206 100644 (file)
--- a/PLC/Table.py
+++ b/PLC/Table.py
@@ -284,7 +284,8 @@ class Row(dict):
         (*) column 2: actual tag value, renamed into tagname
         """
 
-        if not cls.view_tags_name: return ""
+        if not cls.view_tags_name: 
+            raise Exception, 'WARNING: class %s needs to set view_tags_name'%cls.__name__
 
         table_name=cls.table_name
         primary_key=cls.primary_key
@@ -404,7 +405,7 @@ class Table(list):
             tag_columns={}
         else:
             (columns,tag_columns,rejected) = classobj.parse_columns(columns)
-            if not columns:
+            if not columns and not tag_columns:
                 raise PLCInvalidArgument, "No valid return fields specified for class %s"%classobj.__name__
             if rejected:
                 raise PLCInvalidArgument, "unknown column(s) specified %r in %s"%(rejected,classobj.__name__)