use class object in class methods via cls to ensure it cooperates well with subclassing.

fixes UWPCE-PythonCert#98

Author: cewing

resources/session03/learning_journal/learning_journal/models.py

@@ -72,7 +72,7 @@ class User(Base):
     def by_name(cls, name, session=None):
         if session is None:
             session = DBSession
-        return DBSession.query(User).filter(User.name == name).first()
+        return DBSession.query(cls).filter(cls.name == name).first()
 
     def verify_password(self, password):
         manager = Manager()

resources/session03/models.py

@@ -66,5 +66,7 @@ class User(Base):
     password = Column(Unicode(255), nullable=False)
 
     @classmethod
-    def by_name(cls, name):
-        return DBSession.query(User).filter(User.name == name).first()
+    def by_name(cls, name, session=None):
+        if session is None:
+            session = DBSession
+        return DBSession.query(cls).filter(cls.name == name).first()

source/presentations/session03.rst

@@ -89,7 +89,7 @@ Questions About the Homework?
 
         @classmethod
         def by_name(cls, name):
-            return DBSession.query(User).filter(User.name == name).first()
+            return DBSession.query(cls).filter(cls.name == name).first()
 
 `View this model online <https://github.com/cewing/training.python_web/blob/5e02f6f84322145433c515c191679ccf976dcae4/resources/session03/models.py#L62>`_