Custom Filter in Django Admin on Django 1.3 or below

Question

How can I add a custom filter to django admin (the filters that appear on the right side of a model dashboard)? I know its easy to include a filter based on a field of that model, but what about a "calculated" field like this:

class NewsItem(models.Model):     headline = models.CharField(max_length=4096, blank=False)     byline_1 = models.CharField(max_length=4096, blank=True)     dateline = models.DateTimeField(help_text=_("date/time that appears on article"))     body_copy = models.TextField(blank=False)      when_to_publish = models.DateTimeField(verbose_name="When to publish",  blank=True, null=True)      # HOW CAN I HAVE "is_live" as part of the admin filter?  It's a calculated state!!     def is_live(self):         if self.when_to_publish is not None:             if ( self.when_to_publish < datetime.now() ):                 return """ <img alt="True" src="/media/img/admin/icon-yes.gif"/> """         else:             return """ <img alt="False" src="/media/img/admin/icon-no.gif"/> """            is_live.allow_tags = True 

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class NewsItemAdmin(admin.ModelAdmin):     form = NewsItemAdminForm     list_display = ('headline', 'id', 'is_live')     list_filter = ('is_live')  #  how can i make this work?? 

Answer 1

Thanks to gpilotino for giving me the push into the right direction for implementing this.

I noticed the question's code is using a datetime to figure out when its live . So I used the DateFieldFilterSpec and subclassed it.

from django.db import models from django.contrib.admin.filterspecs import FilterSpec, ChoicesFilterSpec,DateFieldFilterSpec from django.utils.encoding import smart_unicode from django.utils.translation import ugettext as _ from datetime import datetime  class IsLiveFilterSpec(DateFieldFilterSpec):     """     Adds filtering by future and previous values in the admin     filter sidebar. Set the is_live_filter filter in the model field attribute     'is_live_filter'.    my_model_field.is_live_filter = True     """      def __init__(self, f, request, params, model, model_admin):         super(IsLiveFilterSpec, self).__init__(f, request, params, model,                                                model_admin)         today = datetime.now()         self.links = (             (_('Any'), {}),             (_('Yes'), {'%s__lte' % self.field.name: str(today),                        }),             (_('No'), {'%s__gte' % self.field.name: str(today),                     }),          )       def title(self):         return "Is Live"  # registering the filter FilterSpec.filter_specs.insert(0, (lambda f: getattr(f, 'is_live_filter', False),                                IsLiveFilterSpec)) 

To use you can put the above code into a filters.py, and import it in the model you want to add the filter to

Answer 2

you have to write a custom FilterSpec (not documentend anywhere). Look here for an example:

http://www.djangosnippets.org/snippets/1051/