Add support for testing of super types

CHANGES.rst

@@ -4,6 +4,14 @@ Changelog
 Here you can see the full list of changes between each SQLAlchemy-Utils release.
 
 
+0.25.0 (2014-03-05)
+^^^^^^^^^^^^^^^^^^^
+
+- Added single table inheritance support for generic_relationship
+- Added support for comparing class super types with generic relationships
+- BC break: In order to support different inheritance strategies generic_relationship now uses class names as discriminators instead of table names.
+
+
 0.24.4 (2014-03-05)
 ^^^^^^^^^^^^^^^^^^^
 

docs/generic_relationship.rst

@@ -29,25 +29,85 @@ Generic relationship is a form of relationship that supports creating a 1 to man
 
 
     # Some general usage to attach an event to a user.
-    us_1 = User()
-    cu_1 = Customer()
+    user = User()
+    customer = Customer()
 
-    session.add_all([us_1, cu_1])
+    session.add_all([user, customer])
     session.commit()
 
     ev = Event()
-    ev.object = us_1
+    ev.object = user
 
     session.add(ev)
     session.commit()
 
     # Find the event we just made.
-    session.query(Event).filter_by(object=us_1).first()
+    session.query(Event).filter_by(object=user).first()
 
     # Find any events that are bound to users.
     session.query(Event).filter(Event.object.is_type(User)).all()
 
 
+Inheritance
+^^^^^^^^^^^
+
+::
+
+    class Employee(self.Base):
+        __tablename__ = 'employee'
+        id = sa.Column(sa.Integer, primary_key=True)
+        name = sa.Column(sa.String(50))
+        type = sa.Column(sa.String(20))
+
+        __mapper_args__ = {
+            'polymorphic_on': type,
+            'polymorphic_identity': 'employee'
+        }
+
+    class Manager(Employee):
+        __mapper_args__ = {
+            'polymorphic_identity': 'manager'
+        }
+
+    class Engineer(Employee):
+        __mapper_args__ = {
+            'polymorphic_identity': 'engineer'
+        }
+
+    class Activity(self.Base):
+        __tablename__ = 'event'
+        id = sa.Column(sa.Integer, primary_key=True)
+
+        object_type = sa.Column(sa.Unicode(255))
+        object_id = sa.Column(sa.Integer, nullable=False)
+
+        object = generic_relationship(object_type, object_id)
+
+
+Now same as before we can add some objects::
+
+    manager = Manager()
+
+    session.add(manager)
+    session.commit()
+
+    activity = Activity()
+    activity.object = manager
+
+    session.add(activity)
+    session.commit()
+
+    # Find the activity we just made.
+    session.query(Event).filter_by(object=manager).first()
+
+
+We can even test super types::
+
+
+    # Find any events that are bound to users.
+    session.query(Activity).filter(Event.object.is_type(Employee)).all()
+
+
 Abstract base classes
 ^^^^^^^^^^^^^^^^^^^^^
 

sqlalchemy_utils/generic.py

@@ -1,6 +1,7 @@
 from collections import Iterable
 
 import six
+import sqlalchemy as sa
 from sqlalchemy.ext.hybrid import hybrid_property
 from sqlalchemy.orm import attributes, class_mapper
 from sqlalchemy.orm import ColumnProperty
@@ -154,8 +155,16 @@ class GenericRelationshipProperty(MapperProperty):
             return ~(self == other)
 
         def is_type(self, other):
-            discriminator = unicode(other.__name__)
-            return self.property._discriminator_col == discriminator
+            mapper = sa.inspect(other)
+            # Iterate through the weak sequence in order to get the actual
+            # mappers
+            class_names = [unicode(other.__name__)]
+            class_names.extend([
+                unicode(submapper.class_.__name__)
+                for submapper in mapper._inheriting_mappers
+            ])
+
+            return self.property._discriminator_col.in_(class_names)
 
     def instrument_class(self, mapper):
         attributes.register_attribute(

tests/generic_relationship/test_single_table_inheritance.py

@@ -142,3 +142,20 @@ class TestGenericRelationship(TestCase):
         statement = self.Event.object.is_type(self.Manager)
         q = self.session.query(self.Event).filter(statement)
         assert q.first() is not None
+
+    def test_compare_super_type(self):
+        manager1 = self.Manager()
+        manager2 = self.Manager()
+
+        self.session.add_all([manager1, manager2])
+        self.session.commit()
+
+        event1 = self.Event(object=manager1)
+        event2 = self.Event(object=manager2)
+
+        self.session.add_all([event1, event2])
+        self.session.commit()
+
+        statement = self.Event.object.is_type(self.Employee)
+        q = self.session.query(self.Event).filter(statement)
+        assert q.first() is not None