added backref() function, allows the creation of a backref where you also send keyword arguments that will be placed on the relation

1 files changed, 41 insertions, 0 deletions

diff --git a/examples/backref/backref_tree.py b/examples/backref/backref_tree.py
new file mode 100644
index 000000000..09598069d
--- /dev/null
+++ b/examples/backref/backref_tree.py
@@ -0,0 +1,41 @@
+from sqlalchemy import *
+import sqlalchemy.attributes as attributes
+
+engine = create_engine('sqlite://', echo=True)
+
+class Tree(object):
+    def __init__(self, name='', father=None):
+        self.name = name
+        self.father = father
+    def __str__(self):
+        return '<TreeNode: %s>' % self.name
+    def __repr__(self):
+        return self.__str__()
+        
+table = Table('tree', engine,
+              Column('id', Integer, primary_key=True),
+              Column('name', String(64), nullable=False),
+              Column('father_id', Integer, ForeignKey('tree.id'), nullable=True),)
+
+assign_mapper(Tree, table,
+              properties={
+     # set up a backref using a string
+     #'father':relation(Tree, foreignkey=table.c.id,primaryjoin=table.c.father_id==table.c.id,  backref='childs')},
+                
+     # or set up using the backref() function, which allows arguments to be passed
+     'childs':relation(Tree, foreignkey=table.c.father_id, primaryjoin=table.c.father_id==table.c.id,  backref=backref('father', uselist=False, foreignkey=table.c.id))},
+            )
+
+table.create()
+root = Tree('root')
+child1 = Tree('child1', root)
+child2 = Tree('child2', root)
+child3 = Tree('child3', child1)
+
+objectstore.commit()
+
+print root.childs
+print child1.childs
+print child2.childs
+print child2.father
+print child3.father