The one thing that is frustrating is it is re-querying the database.
So if I create a simple server side function how would I do that? I am
currently using trunk.
On Feb 2, 8:57 am, Andy <andy.hol...@belator.com> wrote:
> Thanks, that worked like a charm. Look forward to your PyCon
> presentation.
>
> On Feb 2, 12:56 am, Michael Bayer <mike...@zzzcomputing.com> wrote:
>
>
>
> > On Feb 1, 2010, at 9:24 PM, Andy (Zenom) wrote:
>
> > > I don't know if my terminology is correct etc. But the basic idea is
> > > the following.
>
> > > In my model I have something like
>
> > > from mylib.helpers import slugify
>
> > > class MyModel(Base):
> > > __tablename__ = "testing"
>
> > > id = Column(Integer, primary_key)
> > > title = Column(Unicode)
> > > description = Column(Unicode)
>
> > > @property
> > > def slug(self):
> > > return slugify(self.title)
>
> > > Now I want to be able to do something like.
> > > session.query(MyModel.id, MyModel.title, MyModel.slug).all()
>
> > > The table obviously doesn't have a slug column, I just want to return
> > > my title as a "pseudo-column" named slug, with it passed through my
> > > slugify method first.
>
> > > I tried to do something like the following:
>
> > > @synonym_for("title")
> > > @property
> > > def slug(self):
> > > return slugify(self.title)
>
> > > And this did not work. It seems to just return another column just
> > > like title (not sent through slugify first). Any idea how I can do
> > > what I am looking for?
>
> > part of the approach depends on if "slugify" can be defined as a SQL
> > function or if it must be executed in Python. If the latter, you probably
> > want MyModel.slug to resolve into a column that also defines a custom type.
>
> > Assuming its a Python function, note that your column can't be used
> > effectively in a comparison operation, like "MyModel.slug == 'foo'", since
> > the slugify() operation would have to be applied in aggregate.
>
> > Anyway assuming non-SQL function, here's a hack I came up with that will do
> > it:
>
> > from sqlalchemy import *
> > from sqlalchemy.orm import *
> > from sqlalchemy.ext.declarative import declarative_base
> > from sqlalchemy.sql.expression import _UnaryExpression
> > from sqlalchemy.types import UserDefinedType
>
> > Base = declarative_base()
>
> > def slugify(text):
> > return "SLUG !" + text
>
> > class MySlugType(UserDefinedType):
> > def result_processor(self, dialect, coltype):
> > return slugify
>
> > class MyModel(Base):
> > __tablename__ = "testing"
>
> > id = Column(Integer, primary_key=True)
> > title = Column(Unicode)
> > description = Column(Unicode)
>
> > slug = column_property(_UnaryExpression(title, type_=MySlugType()))
>
> > engine = create_engine('sqlite://', echo=True)
> > Base.metadata.create_all(engine)
> > session = sessionmaker(engine)()
>
> > session.add(MyModel(title=u'title', description=u'description'))
> > session.commit()
>
> > print session.query(MyModel.title, MyModel.slug).all()
>
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