Django admin model Inheritance is it possible?

Question

Is inheritance possible in admin Models ?

Like For Example consider the following ,

File : models.py

class AbstractModel ( models.Model ):
    # Meta Information common to all classes
    author = models.ForeignKey(auth.models.User , null = False ,related_name="%(class)s_related_author" ) # The user who created 
    editor = models.ForeignKey(auth.models.User , null = True,related_name="%(class)s_related_editor" ) # The user who last edited                   
    created_at = models.DateTimeField(auto_now_add  = True) # Create Time
    edited_at = models.DateTimeField(auto_now = True) # Modify Time

    class Meta:
                abstract = True


class Topic( AbstractModel ):
    name = models.CharField(max_length = NameMaxLength , unique = True)
    version_number = models.IntegerField(default = 0)
    update_frequency = models.IntegerField()

A similar inheritance does not seem to produce the correct result when used in ModelAdmin

File : admin.py

class Abstract_Admin_Model( admin.ModelAdmin ):
        fields =  ('author' , 'editor' , 'created_at' , 'edited_at')
        readonly_fields = ('author' , 'editor' , 'created_at' , 'edited_at')

        def save_model(self, request, obj, form, change):
                if not change :
                        obj.author = request.user
                else : 
                        obj.editor = request.user
                obj.save()

class Admin_Topic( Abstract_Admin_Model ):
     fields += ('name' , 'version_number' , 'update_frequency')


admin.site.register( Topic , Admin_Topic )

EDIT:

I've modified the above model based on suggestions ,

If the admin.py is like so , I don't get any error , and the model appears on the admin.

class AbstractAdminModel(  admin.ModelAdmin  ):
        pass#fields = ['author' , 'editor' , 'created_at' , 'edited_at']


class Admin_Topic( AbstractAdminModel ):
    pass

admin.site.register( Topic , Admin_Topic )

But If i modify it like so

class AbstractAdminModel(  admin.ModelAdmin  ):
    fields = ['author' , 'editor' , 'created_at' , 'edited_at']


class Admin_Topic( AbstractAdminModel ):
    pass

admin.site.register( Topic , Admin_Topic )

I get the following error :

Here is a stack trace Link

Problem : The model does not even appear on the Admin Page

Extra Info:

using django 1.2.5 with pinax 0.7.2 , Ubuntu 11.04 , python 2.7.1+

Answer 1

Maybe it is bit to late for you for the answer, but I think others can have similar problem - as I did.

Here is my solution - I am not sure if it is proper, but it works for me and non other from above can do the same (assuming that you want a multitable inheritance (non abstract model), as I do)

class SiteEntityAdmin(admin.ModelAdmin):
    fieldsets = [
            (None, {'fields': ['name']}),
    ]


class PhotoAdmin(SiteEntityAdmin):
    fieldsets = [
             ('Photo details', {'fields': ['photo_url', 'description']}),
    ]
    fieldsets.insert(0, SiteEntityAdmin.fieldsets[0])