[Zope-CVS] CVS: Packages/pypes/pypes - identity.py:1.20

[Casey Duncan]

Update of /cvs-repository/Packages/pypes/pypes
In directory cvs.zope.org:/tmp/cvs-serv5633

Modified Files:
	identity.py 
Log Message:
Make sure empty identity set can be iterated without being attached to services


=== Packages/pypes/pypes/identity.py 1.19 => 1.20 ===
--- Packages/pypes/pypes/identity.py:1.19	Tue May 25 22:26:17 2004
+++ Packages/pypes/pypes/identity.py	Thu Jun 10 00:36:39 2004
@@ -153,13 +153,17 @@
         if objs:
             self.update(objs)
     
-    def fromIdSet(cls, idset, copy=False, dbconn=None):
+    def fromIdSet(cls, idset, copy=False, dbconn=None, length=None):
         """Alternate constructor to create an identity set from a btree set
         of identifiers. If copy is true, then the set is copied, otherwise it 
         used by the IdentitySet directly. If a copy is not made, then the
         idset should not be mutated outside of the set. dbconn is a ZODB 
         database connection which allows the set to access services before it 
         is committed.
+        
+        If the application knows the length of the set, it can provide the
+        value in the length argument, otherwise the length will be calculated
+        from idset (which may be more expensive).
         """
         set = cls()
         if copy:
@@ -168,7 +172,9 @@
             set._idset = idset
         if dbconn is not None:
             services.attach(set, dbconn)
-        set._length = Length(len(idset))
+        if length is None:
+            length = len(idset)
+        set._length = Length(length)
         return set
     fromIdSet = classmethod(fromIdSet)
     
@@ -240,12 +246,13 @@
         # If an object in the set is no longer registered None is substituted
         # This iterator is lazy and changing the set during iteration
         # has undefined results
-        identity = services.identity(self)
-        for ident in self._idset.keys():
-            try:
-                yield identity.getObject(ident)
-            except IdentityKeyError:
-                yield None
+        if self._idset:
+            identity = services.identity(self)
+            for ident in self._idset.keys():
+                try:
+                    yield identity.getObject(ident)
+                except IdentityKeyError:
+                    yield None
     
     def union(self, other):
         return self.__class__.fromIdSet(