Django: Cross references

Question

I have the following site structure:

- Windows
    - 98
         - Subpage1
         - Subpage2
    - XP
         - ....
    - 7
    - ....
- Mac
    - 10.7
         - Subpage1
         - Subpage2
    - 10.8
         - ...
    - 10.9
- Ubuntu
    - 13.10

Each OS is a app and I want a extra model for each app which represents a cross reference. The reference can go to any page.

So pseudocode would look like this:

class Reference(models.Model):
     title = models.CharField(_('title'), max_length=200)
     links_to = models.ForeignKey(Windows | Mac | Ubuntu)

I found a view posts about generic relation, but I was not able to use the solutions for my problem.

A link to a good, easy to understand tutorial or any help would be great.

Thanks

Edit:

I thought this might work. But I just can access one property (slug) in this example and not the whole object:

from django.db import models
from itertools import chain

from otherapp.models import Geschaeftsfelder
from otherapp.models import Themenschwerpunkte
from otherapp.models import Themen

from django.utils.translation import ugettext as _
from common.fields import MarkdownTextField, translated_field

class Box(models.Model):

    title = models.CharField(max_length=100)

    headline_de = MarkdownTextField(verbose_name=_(u'Inhaltstext (dt.)'), blank=True)


    geschaeftsfelder = Geschaeftsfelder.objects.values_list('slug', 'title')
    themenschwerpunkte = Themenschwerpunkte.objects.values_list('slug', 'title')
    themen = Themen.objects.values_list('slug', 'title')

    result_list = chain(geschaeftsfelder, themenschwerpunkte, themen)

    links_to      = models.CharField(
                        max_length=200,
                        choices= result_list
                        )

Edit 2: I also tried a solution with generic content types:

When I add the following code to my Box model, I get a dropdown list with the right content types (themenschwerpunkte, geschaeftsfelder, ...).

But I'm still not able to create a link to a specific page.

# http://stackoverflow.com/questions/6335986/how-can-i-restrict-djangos-genericforeignkey-to-a-list-of-models?lq=1
limit = models.Q(app_label = 'geschaeftsfelder', model = 'geschaeftsfelder') | models.Q(app_label = 'geschaeftsfelder', model = 'themenschwerpunkte') | models.Q(app_label = 'geschaeftsfelder', model = 'themen')
content_type = models.ForeignKey(ContentType, limit_choices_to = limit)
object_id = models.PositiveIntegerField()
content_object = generic.GenericForeignKey('content_type', 'object_id')

Edit 3:

Thank you very much for your answers and the time you invested but I'm going to use feinCMS instead of djangoCMS. This is much easier to understand for me and more suitable.

When you say each OS is a separate *app*, presumably you mean they are individual models in different apps. That seems an odd data model: seems like it would be better to have one model to hold the different values for OS. — Daniel Roseman, Oct 31 '13 at 11:22
Well the structure is a little bit different than in my example. Each OS has a different structure. — Alexander Scholz, Oct 31 '13 at 11:28
Maybe I don't unserstand your answer. Can you explain it more detailed or give a example? — Alexander Scholz, Nov 05 '13 at 08:53

score 0 · Answer 1 · answered Nov 05 '13 at 11:09

0

The content type approach seems suitable. The django docs on generic relations are a very good source.

I copy some snipplets of code I was using, maybe they are helpful:

object_id    = models.PositiveIntegerField(blank=True, null=True)
content_type = models.ForeignKey(ContentType, blank=True, null=True, verbose_name="Verweist auf")
of           = generic.GenericForeignKey('content_type', 'object_id' )

In admin, I make use of content types by definig dedicated functions, e.g. one to get all empty relations (in your case: No OS selected)

def get_queryset(self, request):
    qs = super(MyObjectAdmin, self).get_queryset(request)
    return qs.filter(content_type=None)

answered Nov 05 '13 at 11:09

OBu

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Sorry I don't really understand what I have to do. Where do you add the second block of code exactly? – Alexander Scholz Nov 05 '13 at 11:39
This is in my admin.py and in my MyModelAdmin. But similar code will work in other sections as well, I just wanted to show one example where `content_type`was used in some code. In my project, I'm using three different models for organizations / individuals and they are referd by the ContentType ForeignKey. – OBu Nov 05 '13 at 19:56

Django: Cross references

1 Answers1