Added convenience function registry.getRelations()

git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@846 fd906abe-77d9-0310-91a1-e0d9ade77398

relation/README.txt

@@ -280,6 +280,15 @@ It should work also for triadic relations:
   >>> clarkChildren[0].third == kirk
   True
 
+There is also a convenience function that it makes even easier to query
+a relations registry; it allows to query for more than one relationship:
+
+  >>> from cybertools.relation.registry import getRelations
+  >>> len(getRelations(first=clark))
+  2
+  >>> len(getRelations(first=clark, relationships=[LivesIn]))
+  1
+
 
 Handling object removal
 ~~~~~~~~~~~~~~~~~~~~~~~

relation/__init__.py

@@ -60,4 +60,3 @@ class TriadicRelation(Relation):
         self.second = second
         self.third = third
 
-    

relation/registry.py

@@ -129,6 +129,30 @@ class IndexableRelationAdapter(object):
             return value
 
 
+# convenience function:
+
+def getRelations(first=None, second=None, third=None, relationships=None):
+    """ Return a sequence of relations matching the query specified by the
+        parameters.
+
+        The relationships parameter expects a sequence of relationships
+        (relation classes or predicate objects).
+    """
+    registry = zapi.getUtility(IRelationsRegistry)
+    query = {}
+    if first: query['first'] = first
+    if second: query['second'] = second
+    if third: query['third'] = third
+    if not relationships:
+        return registry.query(**query)
+    else:
+        result = set()
+        for r in relationships:
+            query['relationship'] = r
+            result.update(registry.query(**query))
+        return result
+
+
 # events and handlers
 
 class RelationInvalidatedEvent(ObjectEvent):