Pierre B <rocambolesque...@gmail.com> wrote: > I made a type in the Right model, here are the models again:
if you’re referring to the behavior of Right.left when you use it in a query, such as query(Right).join(Right.left), then the “default” value of a Column object has no interaction there. it seems like you probably want to do something very simple here but I’m not getting enough information on what that is. If you could illustrate the usage of the objects that you are looking for, that would help. > > class HasSomeAttribute(object): > @declared_attr.cascading > def type(cls): > if has_inherited_table(cls): > if cls.__name__ == 'MySubClass1': > return db.Column(db.Integer, default=1) > else: > return db.Column(db.Integer, default=2) > else: > return db.Column(db.Integer, default=0) > > class MyClass(HasSomeAttribute, db.Model): > __tablename__ = 'people4l2' > id = db.Column(db.Integer, primary_key=True) > id1 = db.Column(db.Integer) > id2 = db.Column(db.Integer) > > class MySubClass1(MyClass): > pass > > class MySubClass2(MyClass): > pass > > class Right(db.Model): > id = db.Column(db.Integer, primary_key=True) > left = relationship( > 'Left', > secondary= MySubClass1.__table__, > primaryjoin='and_(MySubClass1.type == 802, MySubClass1.id2 == > Right.id)', > secondaryjoin='and_(MySubClass1.type == 802, MySubClass1.id1 == > Left.id)' > ) > > class Left(db.Model): > id = db.Column(db.Integer, primary_key=True) > > > On Tuesday, March 31, 2015 at 12:12:35 PM UTC+2, Pierre B wrote: > Hi Michael, > > Thank you for your response. > Unfortunately I have already tried to use the __init__ function/catch the > init event but I am only referencing the sub classes in a relationship which > does not seem to actually instantiate classes because the __init__ is never > called/init event is never fired. > Here is a simple version of my models. > > class HasSomeAttribute(object): > @declared_attr.cascading > def type(cls): > if has_inherited_table(cls): > if cls.__name__ == 'MySubClass1': > return db.Column(db.Integer, default=1) > else: > return db.Column(db.Integer, default=2) > else: > return db.Column(db.Integer, default=0) > > class MyClass(HasSomeAttribute, db.Model): > __tablename__ = 'people4l2' > id = db.Column(db.Integer, primary_key=True) > id1 = db.Column(db.Integer) > id2 = db.Column(db.Integer) > > class MySubClass1(MyClass): > pass > > class MySubClass2(MyClass): > pass > > class Right(db.Model): > id = db.Column(db.Integer, primary_key=True) > subclass_attr = relationship( > 'Contact', > secondary= MySubClass1.__table__, > primaryjoin='and_(MySubClass1.type == 802, MySubClass1.id2 == > Right.id)', > secondaryjoin='and_(MySubClass1.type == 802, MySubClass1.id1 == > Left.id)' > ) > > class Left(db.Model): > id = db.Column(db.Integer, primary_key=True) > > MyClass is used as a junction table for a bunch of different relationships, > the type field is used to differentiate the relationships. > > > On Monday, March 30, 2015 at 5:26:30 PM UTC+2, Michael Bayer wrote: > > > Pierre B <rocambol...@gmail.com> wrote: > > > Hi all, > > > > I'm ultimately trying to have different default values for the same column. > > Following the documentation, the @declared_attr.cacading decorator seems to > > be the best approach. > > Here's my code: > > class HasSomeAttribute(object): > > @declared_attr.cascading > > def type(cls): > > if has_inherited_table(cls): > > if cls.__name__ == 'MySubClass1': > > return db.Column(db.Integer, default=1) > > else: > > return db.Column(db.Integer, default=2) > > else: > > return db.Column(db.Integer, default=0) > > > > class MyClass(HasSomeAttribute, db.Model): > > __tablename__ = 'people4l2' > > id = db.Column(db.Integer, primary_key=True) > > > > class MySubClass1(MyClass): > > pass > > > > class MySubClass2(MyClass): > > pass > > > > I iterated quite a few times over this but I'm systematically getting this > > error: > > ArgumentError: Column 'type' on class <class '__main__.MySubClass1'> > > conflicts with existing column 'people4l2.type’ > > this mapping illustrates MySubClass1 and MySubClass2 as both sharing the > same table “people4l2”, as they have no __tablename__ attribute, so there > can only be one “type” column. So in this case it is not appropriate to use > cascading in exactly this way, as MyClass already has a “type” column, and > that gets attached to the “people4l2” table and that’s it; there can be no > different “type” column on MySubClass1/MySubClass2. > > If you’d like “type” to do something different based on which class is being > instantiated, this is an ORM-level differentiation. Use either the > constructor __init__() to set it or use the init() event > (http://docs.sqlalchemy.org/en/rel_0_9/orm/events.html?highlight=event%20init#sqlalchemy.orm.events.InstanceEvents.init). > > > OTOH if “type” is actually the “polymoprhic discriminator”, which is what > this looks like, then you’d be looking to just set up “type” as the > “polymorphic_on” column and set up the “1”, “2”, “0” as the polymorphic > identity (see > http://docs.sqlalchemy.org/en/rel_0_9/orm/inheritance.html#single-table-inheritance > > for a simple example). > > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at http://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
