Question

How can I get at the Labels data from within my Task model?

class Task(db.Model):
  title = db.StringProperty()

class Label(db.Model):
  name = db.StringProperty()

class Tasklabel(db.Model):
  task = db.ReferenceProperty(Task)
  label = db.ReferenceProperty(Label)

creating the association is no problem, but how can I get at the labels associated with a task like:

task = Task.get('...')
for label in task.labels

Answer 1

Don’t you want a ListProperty on Task like this to do a many-to-many?

class Label(db.Model)
   name = db.StringProperty()

   @property
   def members(self):
      return Task.gql("WHERE labels = :1", self.key())

class Task(db.Model)
   title = db.StringProperty();
   labels = db.ListProperty(db.Key)

Then you could do

foo_label = Label.gql("WHERE name = 'foo'").get()
task1 = Task.gql("WHERE title = 'task 1'").get()
if foo_label.key() not in task1.labels:
  task1.labels.append(foo_label.key())
task1.put()

There’s a thorough article about modeling entity relationships on Google code. I stole the code above from this article.