Models must explicitly inherit from SurrogatePK to add primary key

{{cookiecutter.app_name}}/tests/test_models.py

@@ -10,6 +10,13 @@ from .factories import UserFactory
 @pytest.mark.usefixtures('db')
 class TestUser:
 
+    def test_get_by_id(self):
+        user = User('foo', 'foo@bar.com')
+        user.save()
+
+        retrieved = User.get_by_id(user.id)
+        assert retrieved == user
+
     def test_created_at_defaults_to_datetime(self):
         user = User(username='foo', email='foo@bar.com')
         user.save()

{{cookiecutter.app_name}}/{{cookiecutter.app_name}}/database.py

@@ -6,6 +6,7 @@ from sqlalchemy.orm import relationship
 
 from .extensions import db
 
+# Alias common SQLAlchemy names
 Column = db.Column
 relationship = relationship
 
@@ -13,18 +14,6 @@ class CRUDMixin(object):
     """Mixin that adds convenience methods for CRUD (create, read, update, delete)
     operations.
     """
-    __table_args__ = {'extend_existing': True}
-
-    id = db.Column(db.Integer, primary_key=True)
-
-    @classmethod
-    def get_by_id(cls, id):
-        if any(
-            (isinstance(id, basestring) and id.isdigit(),
-             isinstance(id, (int, float))),
-        ):
-            return cls.query.get(int(id))
-        return None
 
     @classmethod
     def create(cls, **kwargs):
@@ -50,10 +39,38 @@ class CRUDMixin(object):
         db.session.delete(self)
         return commit and db.session.commit()
 
+class Model(CRUDMixin, db.Model):
+    """Base model class that includes CRUD convenience methods."""
+    __abstract__ = True
+
 # From Mike Bayer's "Building the app" talk
 # https://speakerdeck.com/zzzeek/building-the-app
-def ReferenceCol(tablename, nullable=False, **kwargs):
+class SurrogatePK(object):
-    """Column that adds primary key foreign key reference."""
+    """A mixin that adds a surrogate integer 'primary key' column named
+    ``id`` to any declarative-mapped class.
+    """
+    __table_args__ = {'extend_existing': True}
+
+    id = db.Column(db.Integer, primary_key=True)
+
+    @classmethod
+    def get_by_id(cls, id):
+        if any(
+            (isinstance(id, basestring) and id.isdigit(),
+             isinstance(id, (int, float))),
+        ):
+            return cls.query.get(int(id))
+        return None
+
+
+def ReferenceCol(tablename, nullable=False, pk_name='id', **kwargs):
+    """Column that adds primary key foreign key reference.
+
+    Usage: ::
+
+        category_id = ReferenceCol('category')
+        category = relationship('Category', backref='categories')
+    """
     return db.Column(
-        db.ForeignKey("{0}.id".format(tablename)),
+        db.ForeignKey("{0}.{1}".format(tablename, pk_name)),
         nullable=nullable, **kwargs)

{{cookiecutter.app_name}}/{{cookiecutter.app_name}}/user/models.py

@@ -5,15 +5,16 @@ from flask.ext.login import UserMixin
 
 from {{cookiecutter.app_name}}.extensions import bcrypt
 from {{cookiecutter.app_name}}.database import (
+    Column,
     db,
-    CRUDMixin,
+    Model,
     ReferenceCol,
     relationship,
-    Column,
+    SurrogatePK,
 )
 
 
-class Role(CRUDMixin, db.Model):
+class Role(SurrogatePK, Model):
     __tablename__ = 'roles'
     name = Column(db.String(80), unique=True, nullable=False)
     user_id = ReferenceCol('users', nullable=True)
@@ -22,7 +23,7 @@ class Role(CRUDMixin, db.Model):
     def __init__(self, name, **kwargs):
         db.Model.__init__(self, name=name, **kwargs)
 
-class User(UserMixin, CRUDMixin,  db.Model):
+class User(UserMixin, SurrogatePK, Model):
 
     __tablename__ = 'users'
     username = Column(db.String(80), unique=True, nullable=False)