Hi guys,
I've got a question regarding the association object pattern. Though
perhaps it's not what I should be using...
Let's say I've got a Parent class that I'd like to add tags with data to.
class Parent(Base)
id = Str
# The association object
class Tag(Base)
parent_id = Str
child_id = Int
value = Float
# The child object, comes with some data too
class Child(Base)
id = Int
name = Str
date = Date
The relation setup is just like in the example in the docs.
So now I'd like to create a set of tags and pass the info the tag
needs to create its child to its constructor.
tags = [Tag(name='name1', date=dt.date.today()), ...etc. ]
Then do something like:
parent = Parent()
for tag in tags:
parent.tags.append(tag) # can I use a set here instead of a list?
The bit that I'm struggeling with is duplicate tag objects...
In the tag's constructor I have:
child = sess.query(Child).filter(Child.name ==
name).filter(Child.date == date).first()
if child is None:
child = Child(name=name, date=date)
self.child = child
So if there's a child object in the db with the same name and date it
uses that as it's child field.
Though I'm getting : raise exc.FlushError("New instance %s with
identity key %s conflicts with persistent instance %s" %
(state_str(state), str(instance_key), state_str(existing)))
Which means the tag I'm adding is allready in the db. Which is true.
Normally I'd use merge to get around that, but don't know how to do
that since I'm 'adding' the new instance through parent.tags.append()
Any ideas how to solve this? Am I simply using the wrong approach?
Regards,
Christian
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