modernize adjacency list example, use declarative

diff --git a/examples/adjacency_list/adjacency_list.py b/examples/adjacency_list/adjacency_list.py
index bac43f09711fb2320f048a4b9264e436bc6285d5..91c6e1ccfbc7bd3d506221ce2c0f3eed438a032b 100644 (file)
--- a/examples/adjacency_list/adjacency_list.py
+++ b/examples/adjacency_list/adjacency_list.py
@@ -1,46 +1,21 @@
 from sqlalchemy import MetaData, Table, Column, Sequence, ForeignKey,\
                         Integer, String, create_engine
 
-from sqlalchemy.orm import sessionmaker, mapper, relationship, backref,\
+from sqlalchemy.orm import sessionmaker, relationship, backref,\
                                 joinedload_all
-
+from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.orm.collections import attribute_mapped_collection
 
-metadata = MetaData()
 
-tree_table = Table('tree', metadata,
-    Column('id', Integer, primary_key=True),
-    Column('parent_id', Integer, ForeignKey('tree.id')),
-    Column('name', String(50), nullable=False)
-)
+Base = declarative_base()
 
-class TreeNode(object):
-    def __init__(self, name, parent=None):
-        self.name = name
-        self.parent = parent
+class TreeNode(Base):
+    __tablename__ = 'tree'
+    id = Column(Integer, primary_key=True)
+    parent_id = Column(Integer, ForeignKey(id))
+    name = Column(String(50), nullable=False)
 
-    def append(self, nodename):
-        self.children[nodename] = TreeNode(nodename, parent=self)
-
-    def __repr__(self):
-        return "TreeNode(name=%r, id=%r, parent_id=%r)" % (
-                    self.name,
-                    self.id,
-                    self.parent_id
-                )
-
-def dump_tree(node, indent=0):
-
-    return "   " * indent + repr(node) + \
-                "\n" + \
-                "".join([
-                    dump_tree(c, indent +1) 
-                    for c in node.children.values()]
-                )
-
-
-mapper(TreeNode, tree_table, properties={
-    'children': relationship(TreeNode, 
+    children = relationship("TreeNode", 
 
                         # cascade deletions
                         cascade="all",
@@ -48,25 +23,45 @@ mapper(TreeNode, tree_table, properties={
                         # many to one + adjacency list - remote_side
                         # is required to reference the 'remote' 
                         # column in the join condition.
-                        backref=backref("parent", remote_side=tree_table.c.id),
+                        backref=backref("parent", remote_side=id),
 
                         # children will be represented as a dictionary
                         # on the "name" attribute.
                         collection_class=attribute_mapped_collection('name'),
                     )
-    })
+
+    def __init__(self, name, parent=None):
+        self.name = name
+        self.parent = parent
+
+    def __repr__(self):
+        return "TreeNode(name=%r, id=%r, parent_id=%r)" % (
+                    self.name,
+                    self.id,
+                    self.parent_id
+                )
+
+    def dump(self, _indent=0):
+
+        return "   " * _indent + repr(self) + \
+                    "\n" + \
+                    "".join([
+                        c.dump(_indent +1) 
+                        for c in self.children.values()]
+                    )
 
 if __name__ == '__main__':
     engine = create_engine('sqlite://', echo=True)
 
-    def msg(msg):
-        print "\n\n\n" + "-" * len(msg)
+    def msg(msg, *args):
+        msg = msg % args
+        print "\n\n\n" + "-" * len(msg.split("\n")[0])
         print msg
-        print "-" * len(msg)
+        print "-" * len(msg.split("\n")[0])
 
     msg("Creating Tree Table:")
 
-    metadata.create_all(engine)
+    Base.metadata.create_all(engine)
 
     # session.  using expire_on_commit=False
     # so that the session's contents are not expired
@@ -74,31 +69,27 @@ if __name__ == '__main__':
     session = sessionmaker(engine, expire_on_commit=False)()
 
     node = TreeNode('rootnode')
-    node.append('node1')
-    node.append('node3')
+    TreeNode('node1', parent=node)
+    TreeNode('node3', parent=node)
 
     node2 = TreeNode('node2')
-    node2.append('subnode1')
+    TreeNode('subnode1', parent=node2)
     node.children['node2'] = node2
-    node.children['node2'].append('subnode2')
+    TreeNode('subnode2', parent=node.children['node2'])
 
-    msg("Created new tree structure:")
-
-    print dump_tree(node)
+    msg("Created new tree structure:\n%s", node.dump())
 
     msg("flush + commit:")
 
     session.add(node)
     session.commit()
 
-    msg("Tree After Save:")
-
-    print dump_tree(node)
+    msg("Tree After Save:\n %s", node.dump())
 
-    node.append('node4')
-    node.children['node4'].append('subnode3')
-    node.children['node4'].append('subnode4')
-    node.children['node4'].children['subnode3'].append('subsubnode1')
+    TreeNode('node4', parent=node)
+    TreeNode('subnode3', parent=node.children['node4'])
+    TreeNode('subnode4', parent=node.children['node4'])
+    TreeNode('subsubnode1', parent=node.children['node4'].children['subnode3'])
 
     # mark node1 as deleted and remove
     session.delete(node.children['node1'])
@@ -106,14 +97,11 @@ if __name__ == '__main__':
     msg("Removed node1.  flush + commit:")
     session.commit()
 
-    print "\n\n\n----------------------------"
-    print "Tree After Save:"
-    print "----------------------------"
-
     # expire the "children" collection so that
     # it reflects the deletion of "node1".
     session.expire(node, ['children'])
-    print dump_tree(node)
+
+    msg("Tree after save:\n %s", node.dump())
 
     msg("Emptying out the session entirely, "
         "selecting tree on root, using eager loading to join four levels deep.")
@@ -124,8 +112,7 @@ if __name__ == '__main__':
                         filter(TreeNode.name=="rootnode").\
                         first()
 
-    msg("Full Tree:")
-    print dump_tree(node)
+    msg("Full Tree:\n%s", node.dump())
 
     msg( "Marking root node as deleted, flush + commit:" )