top-level model
berto
I'm just starting with django and am trying to figure out the best way
to approach creating a top-level model. My "Item" model would be one
that all other items will extend in some way. By doing this, i'm
hoping to give all entries an owner, some metadata (e.g. timestamp) and
per-entry permissions. My item model currently looks like:
class Item(meta.Model):
pub_date = meta.DateTimeField('Publish Date', auto_now_add=True)
owner = meta.ForeignKey(User)
parent = meta.ForeignKey('self', null=True, blank=True,
related_name='child')
def __repr__(self):
return "%s on %s" % (self.owner, self.pub_date)
class META:
permissions = (
("view_item", "Can view item"),
)
class ItemPermission(meta.Model):
item = meta.ForeignKey(Item)
user = meta.ForeignKey(User)
permission = meta.ForeignKey(Permission)
The first item I want to create is a Note, so my model starts like
this:
class Note(meta.Model):
subject = meta.CharField(maxlength=120, core=True)
text = meta.TextField(core=True)
def __repr__(self):
return self.subject
class META:
admin = meta.Admin()
The problem I run into is how to link an item to my Note model. I've
tried a few things such as extending the Note class:
class Note(Item)
This doesn't work because the item columns are recreated in the
database, not referenced. So, I tried the following:
item = meta.ForeignKey(Item, edit_inline=meta.STACKED
num_in_admin=1)
as well as:
item = meta.OneToOneField(Item, primary_key=True, blank=True)
I learned that the former attempt is wrong since it's the reverse of
what I'm trying to accomplish. Instead of giving me an item form when
I add a note, the Item model gets a note form.
The latter almost works, but I still don't get a way to edit an item
inline.
Currently my two goals are:
- ability to manipulate Item data when viewing a note in the admin
interface
- ability to give each entry user and group permissions (not even
attempted yet).
Any advice is greatly appreciated.
Thanks!
-berto.
Alice
http://groups.google.com/group/django-users/browse_thread/thread/89123a476f7a26ac
more information on the one-to-one relationship can be found here:
http://groups.google.com/group/django-users/browse_thread/thread/cb3c96aaffc42597/e10e4aec10e81c96?q=subclass&rnum=1#e10e4aec10e81c96
there is no answer for it yet (if there is, I'd love to hear it ...)
for your permissions issue, you should look into Django's builtin
support for Users, user authentication and permissions:
http://www.djangoproject.com/documentation/authentication/#id5
The documentation is still thin and patchy in a lot of places, but it
should be treated as more of a reference to the code.
Hope this helps some,
Alice
Roberto Aguilar
I think our problems are the same, just that you are looking at it
from the left side and I'm looking from the right. ;) In fact, I was
so confused when you replied to the one-to-one post as I thought you
were replying to me!
"""
This relationship has been modelled as a one-to-one, but when listing
the detail of any given Item, I would dearly like to have the extended
data displayed too - whatever that may be. The problem is I can't
figure out how to detect that extra data without adding some
indication in the Items table as to what other table(s) to check in.
Or I could check all specialized tables, which is clunky.
"""
I think part of the solution would be adding a type column to the item
database. To follow your example, type's value for a book would be
"BookItem" (this would be better as a fully-qualified name
items.BookItem if your app was called items). At this point it would
be trivial for the admin to do a lookiup in the bookitems specialized
table. One limitation I can see is when adding a new item from the
item admin page. At that point the page doesn't know the type of item
you're trying to add.
The way I am looking at the problem is whenever I go to the Book
Item's admin page, I would see and be able to fill out the base item's
information as well in the same form, in one shot. This is very
similar to the concept in the Polls tutorial, where you can add many
choices from the Poll view by setting up the relation:
poll = meta.ForeignKey(Poll, edit_inline=meta.STACKED, num_in_admin=3)
except that this doesn't work when you have many items being extended;
you would get the information for all items in the item view, which is
not the desired result.
Here's a possible solution I've been thinking about. Maybe adding a
keyword argument similar to edit_inline, "parent_edit_inline", which
would pull the parent table into the child form instead of the other
way around.
This relationship would not need the keyword "num_in_admin" because
there could only be one parent, and you would simply set the
parent_edit_inline to True, since TABULAR would make no sense.
Another field type, "ChildDescriptionField", could be added so that
adding a BookItem would fill in that column with the child's type
(BookItem).
The result would look something like:
class Item(meta.Model):
type = meta.ChildDescriptionField()
class BookItem(meta.Model):
item = meta.ForeignKey(Item, parent_edit_inline=True)
[...]
Does this ramble sound feasible/the right direction to go in?
-Roberto.