determining if a one-to-many relation exists

[Jim N]

Hi Djangoists,

I have a model "question" which has a one-to-many relationship with
"answer".

class Question(models.Model):
text = models.TextField()

class Answer(models.Model):
text = models.TextField()
question = models.ForeignKey(Question)

I can't figure out how to construct a filter that will give me

- just questions where there isn't an answer
- just questions where there is an answer

Is this really easy and I'm just not seeing it?

Thanks,
Jim

[Jim N]

Just to clarify, I'm trying to filter questions that have an answer,
but I don't know the particular answer. I just want to determine
whether or not an answer object exists, with the foreign key of this
question.

I could do

Answer.objects.filter(question = my_question)

but I am filtering questions on a number of parameters, such as text
of the question.

Thanks,
Jim

[Nick Serra]

You could query like this:

Question.objects.filter(answer__isnull=False)

This would give you a set of questions where an answer exists. Setting
it to True would give you a set where answers don't exist.

[Jim N]

Yes! That's it! Thank you.

[Nick Serra]

Welcome! You might just want to incorporate the answer into the
question model, and then do a boolean field for is_answered for quick
reference. The thought of multiple answers for one question seems odd,
and use of one-to-one fields isn't recommended, so i'd just keep it in
one model l)