Hi Paul,
You've got a couple of options for this. The first uses inheritance:
class Node(models.Model):
parent = models.ForeignKey("Node", blank=True, null=True,
related_name="children")
class Job(Node):
pass
class Shot(Node):
pass
The second uses generic foreign keys:
class Job(models.Model):
parent_type = models.ForeignKey("contenttypes.ContentType")
parent_id = models.PositiveIntegerField(db_index=True)
parent = GenerticForeignKey("parent_type", "parent_id")
class Shot(models.Model):
parent_type = models.ForeignKey("contenttypes.ContentType")
parent_id = models.PositiveIntegerField(db_index=True)
parent = GenerticForeignKey("parent_type", "parent_id")
Personally, I'd go with the first, as it will integrate better with the
Djano admin application. To traverse the tree, use the Node model.
Once you have got to your required location in the tree, use node.job or
node.shot to get the rest of the information.
David.
paul wrote:
> hi,
>
> I'm designing my first django app and would appreciate any advice how
> best to organise my models.
>
> I have a hierarchal model called Node. this allows me to create a
> hierarchy of nodes - and perform hierarchal operatoins. So far so
> good. each node can be of two 'types':
> 1/ job
> 2/ shot
>
> I did originally try and make shot & job inherit the Node model.
> However, they couldn't 'link' together (ie, using self as a
> ForeignKey) - as they're of different types. So i've made each of
> these two node types into seperate models. each Node should only be
> linked to one type at a time. From the manual/book - i belive that
> GenericForeignKey is the way to go. ie, insert a GenericForeignKey
> field into the Node. Does this sound like a good approach?
>
> Many Thanks in Advance,
>
> Paul
> >
--
David Hall
Technical Lead
Etianen.com
Tel: 07896 106290
Email [EMAIL PROTECTED]
Web www.etianen.com
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