list_display does not allow functions of referenced objects

Sorry; the third example should have two underline characters between "foreign" and "method".

There is no need to support functions on ForeignKey models. You can encapsulate that in a function on the model.

Thanks for the quick reply, which I have implemented for now.

Still, your proposal violates DRY: I have to define the same function on each model that references the foreign model.

Seems like a reasonable addition to me. Do we even allow doing this for actual fields of a related model? This feature probably needs to be part of newforms-admin or wait until that branch is merged though. It would be helpful if you could attach a simple example, or even try your hand at creating a patch.

I just wanted to raise this again. I'm using the new forms admin branch and it's odd that in the following

class BlueEDIJobFileAdmin(admin.ModelAdmin):
    search_fields=('blueedijob__client__code',)
    list_display = ('id','blueedijob__client__code',)

The search_fields option is valid, but the list_display option is not.

I want to raise it once again since newforms-admin is now in...

patch to regressiontests.modeladmin with a test that I would like to work

Allow double underscore style access to related object fields in list_display

The patch uploaded shows the related objects field values in the same way as the object field values are shown (a boolean as an tick icon etc.) rather than as a string as a custom method would.

However the header of the field still shows the related object's verbose name. Ideally it would show something like (section -> title) to indicate its a related objects field, but I haven't worked out how to do that yet :)

What is the next step to see this patch in django?

thanks

Replying to pihentagy:

What is the next step to see this patch in django?

Since this ticket was raised callables were added to the list of things allowed, in list_display, as were methods on ModelAdmin, in [8352]. Do we need yet another way to specify something in list_display? Can this case not be covered by callables?

I was going to experiment to see, but I can't. First, the patch doesn't apply cleanly to existing trunk. The actual apply failures are on the tests, not the code, so I thought I could experiment with the code, but I can't get that to work either. If I add something with the double underscore syntax to the list_display for one of the models in my app, I get an ImproperlyConfigured exception thrown during admin validation:

Traceback:
File "/home/kmt/django/trunk/django/core/handlers/base.py" in get_response
  77.                     request.path_info)
File "/home/kmt/django/trunk/django/core/urlresolvers.py" in resolve
  179.             for pattern in self.urlconf_module.urlpatterns:
File "/home/kmt/django/trunk/django/core/urlresolvers.py" in _get_urlconf_module
  198.             self._urlconf_module = __import__(self.urlconf_name, {}, {}, [''])
File "/home/kmt/software/web/xword/../xword/urls.py" in <module>
  9. admin.autodiscover()
File "/home/kmt/django/trunk/django/contrib/admin/__init__.py" in autodiscover
  40.         __import__("%s.admin" % app)
File "/home/kmt/software/web/xword/../xword/crossword/admin.py" in <module>
  61. admin.site.register(Puzzles, PuzzlesAdmin)
File "/home/kmt/django/trunk/django/contrib/admin/sites.py" in register
  76.             validate(admin_class, model)
File "/home/kmt/django/trunk/django/contrib/admin/validation.py" in validate
  38.                                 % (cls.__name__, idx, field, cls.__name__, model._meta.object_name))

Exception Type: ImproperlyConfigured at /admin/crossword/authors/
Exception Value: PuzzlesAdmin.list_display[4], 'AuthorID__Notes' is not a callable or an attribute of 'PuzzlesAdmin' or found in the model 'Puzzles'.

This may be validation code added since the patch was originally created, I don['t know -- I think I specified the new thing correctly but I'm not entirely sure because there are no docs for the new supported thing in list_display. The existing docs spell out pretty clearly what's allowed: http://docs.djangoproject.com/en/dev/ref/contrib/admin/#list-display and they would also need to be updated if it's decided this addition is still worthwhile.

So a working patch with docs that applies cleanly to trunk (and doesn't have the same problem with sorting that [8352] introduced, see [9212]), plus something that addresses graham's last remark about the title for the column being non-intuitive, are all missing for this to get in...but even before that please answer the first question I had: what does this provide that isn't already possible given the expanded options of things you can now specify in list_display?

Replying to kmtracey:

but even before that please answer the first question I had: what does this provide that isn't already possible given the expanded options of things you can now specify in list_display?

Consistency and DRY: so you shouldn't write boilerplate code. You shouldn't specify column name django alredy knows.

Replying to pihentagy:

Consistency and DRY: so you shouldn't write boilerplate code. You shouldn't specify column name django alredy knows.

I understand wanting to avoid boilerplate code but I'm missing how this is a common enough case to warrant inclusion and balance the additional complexity (both for users -- the list of things you can put in list_display is getting a bit long -- and code maintainers). What's the common situation where user's would really like to see the value of a field in a related model instead of just the text representation of the related model? I'm just not seeing that as a very common need, meaning when you need it if you have to write a little extra code it's no big deal. It's not boilerplate if you only have to do it in rare situations. I'm looking for something a little more concrete as motivation than mom and apple pie goodness.

Replying to kmtracey:

Replying to pihentagy:

Consistency and DRY: so you shouldn't write boilerplate code. You shouldn't specify column name django alredy knows.

I understand wanting to avoid boilerplate code but I'm missing how this is a common enough case to warrant inclusion and balance the additional complexity (both for users -- the list of things you can put in list_display is getting a bit long -- and code maintainers). What's the common situation where user's would really like to see the value of a field in a related model instead of just the text representation of the related model? I'm just not seeing that as a very common need, meaning when you need it if you have to write a little extra code it's no big deal. It's not boilerplate if you only have to do it in rare situations. I'm looking for something a little more concrete as motivation than mom and apple pie goodness.

If you have just 1 or 2 foreign keys, you have a lot of place, so it seems logical to display more interesting fields from a foreignkey. The unicode representation is ok, but it is just 1 column, you will find things quickly, if you have 2 or 3 fields from a foreign tabble (not to mention, you will be able to sort on that field for free!)

For example m2m tables with additional fields doesn't contain interesting information on their own. Maybe you want to display more columns from one FK and sort on them...

Replying to pihentagy:

What's the common situation where user's would really like to see the value of a field in a related model instead of just the text representation of the related model? I'm just not seeing that as a very common need, meaning when you need it if you have to write a little extra code it's no big deal. It's not boilerplate if you only have to do it in rare situations. I'm looking for something a little more concrete as motivation than mom and apple pie goodness.

Can I add that I would very much like this functionality for my project. In fact the lack of this functionality led me to give up on the admin interface and create my own thing that did do that!

Being able to mix-in related model fields is very useful for creating a 'dashboard' style admin page which I would think is a very common requirement.

Replying to danros:

Can I add that I would very much like this functionality for my project. In fact the lack of this functionality led me to give up on the admin interface and create my own thing that did do that!

It was easier to write your own admin than write some trivial ModelAdmin methods that returned the information you were interested in?

Khm, sorry for the noise guys, I think I misread this ticket.

All I want to do is:

list_display = ('foreign_key__related_fieldname1', 'foreign_key__related_fieldname2')

so displaying related fields. Should I open a ticket for that, or is there one for it?

Replying to pihentagy:

Should I open a ticket for that, or is there one for it?

I believe that is what this ticket is asking for, so no need for another ticket. In the absence of a working patch for this ticket, you can achieve what you want by adding ModelAdmin methods (or callables) that return the information you are looking for, and specifying these methods in your list_display. It is not particularly difficult and not a lot of code. Doc is here: http://docs.djangoproject.com/en/dev/ref/contrib/admin/#list-display

I'd say this ticket can be closed (I found it when looking for material related to #10230).

Using callables (bare functions for example, i.e. no model methods nor ModelAdmin subclasses methods) make the "It violates DRY: I have to define the same function on each model that references the foreign model" argument moot.

Also, when it comes to the HTML table headers:

1. Seeing a bare 'Code' header (using the comment 6 example) that refers to a code field of a Client model that is located one or more FK-hops away isn't necessarily a good idea, it can be confusing because the user could assume it refers about a (non-existent) code field local to the model being displayed.
2. In the case of more that one level of indirection, having an automatically-generated 'Hop1 Model > ... > HopN Model > Field' header wouldn´t be practical/scalable.

It's more practical in that case that the developer sets explicitely an appropiate, unambiguous header literal using the .short_description facility.

In other words, I'd say current functionality plus a bit of work satisfy the needs expressed in this ticket discussion for this arguably rare scenario.

Reasons not to close this ticket:

• consistency between search_fields, list_display, and list_filter: it seems reasonable to want them all to work the same way. At the basic level, they are all a list of fields, after that, the limitations seem arbitrary (i.e. it seems at first glance as if the more advanced features of each could be available but just haven't been programmed yet).

• this need isn't really so rare, particularly if you have models that relate one-to-one, where you naturally do want to include fields from across several tables.

Would someone like to review the snippet I've come up with as a "work around" of sorts? It would definitely need some work before it could be used in Django if it's deemed worthy, but I hope it's an option at least... I'm not sure I feel comfortable posting it as a patch because of the issues involved with my approach, but I still think it's worth looking at.

You can find it here, along with some details about the issues involved: http://www.codekoala.com/blog/2009/feb/27/model-relationships-and-list_display/

Thanks!

oops... didn't mean to adjust the ticket properties like that.

One thing that I think no one has pointed out yet; if it were possible to set table__field in list_display, you could order the list by that field in the interface, which you can't do with callables.

Replying to haffi67:

One thing that I think no one has pointed out yet; if it were possible to set table__field in list_display, you could order the list by that field in the interface, which you can't do with callables.

You can set admin_order_field on a callable to specify ordering; doc on that is the last bullet under http://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.list_display. If that doesn't currently support the double-underscore syntax to reference a ordering by a field in a related object, then I doubt it would 'just work' for things specified that way in list_display.

Seems like discussion of this has petered out. Too bad, especially when more and more people are looking to subclass parts of admin for their own use.

This is so simple in many other ways in admin. I realize it leads to situations where what you get back isn't a field, but another queryset, but the developer gets what they deserve in that case. Its not hard (or even out of precedent) to simply ignore relations which are nonsense. Just take a look at the behavior of select_related! Having to create a custom method each time is tedious and this limitation prevents extensibility in situations where you've put those fields on the model yourself manually using extra() and other methods.