How to use primary key as an attribute

[Aamu Padi]

This may be a lame question, but how do I use the primary key as a default value for an attribute?

This is my models.py:

    class Thread(models.Model):
        thread_pk = models.PositiveIntegerField(default=self.pk)

This gives me an error:

    self is not defined

How do I go about using the pk as a default value of an attribute? Any help will be grateful. Thank you.

[Timothy W. Cook]

I'm not sure what you are trying to accomplish. Since the 'pk' field
is going to be defined on your instances anyway, do you need a
'thread_pk' field?

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[Aamu Padi]

Actually I need to use Thread class in other class as a ForeignKey. Here is the whole code:

class Thread(models.Model):
    thread_pk = models.PositiveIntegerField(default=self.pk)

class ThreadParticipant(models.Model):
    thread = models.ForeignKey(Thread)
    user = models.ForeignKey(User)

class Message(models.Model):
    thread = models.ForeignKey(Thread)
    sent_date = models.DateTimeField(default=datetime.now)
    body = models.TextField()
    user = models.ForeignKey(User)

Is there anyway to create a new message without manually creating a Thread. I mean to auto-populate the Thread, whenever I create a new Message?

[Timothy W. Cook]

If I understand what you are building. You want some way to group
messages into threads? I assume that a Thread will have many messages?
Unless I am missing something you might want something like this:

class Thread(models.Model):
subject = models.CharField(max_length=256)

class Message(models.Model):
thread = models.ForeignKey(Thread)
sent_date = models.DateTimeField(default=datetime.now)
body = models.TextField()
user = models.ForeignKey(User)

Then you can create a filter for the Thread based on a subject:

selected_subject = Thread.objects.filter(subject="some subject")

Then when you create the message you can use thread =
selected_subject[0] (assuming unique subjects/threads) when you create
your message. OR if 'some subject' isn't found, len(selected_subject)
== 0 then create a new Thread.

HTH,
Tim

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[Aamu Padi]

You are really are a life saver. Thank you so much sir. I have posted a more specific question. Please kindly have a look at it.

Thank you.

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