Django 1.3及以下版本的Admin自定义过滤器

Question

我想知道怎么在Django的管理后台添加一个自定义过滤器（就是在模型仪表盘右侧出现的那些过滤器）。我知道基于模型字段的过滤器很简单，但如果是像这样“计算出来的”字段呢：

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

---

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

Answer 1

在现在的Django开发版本中，支持自定义过滤器。你可以在这里找到相关的说明：https://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.list_filter

Answer 2

你需要写一个自定义的 FilterSpec（这个在文档里没有说明）。

可以看看这里的例子：

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

Answer 3

感谢gpilotino给我指明了实现这个功能的方向。

我发现问题中的代码是用日期时间来判断它是否处于活动状态。所以我使用了DateFieldFilterSpec，并对它进行了子类化。

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))

要使用这个代码，你可以把上面的代码放到一个叫filters.py的文件里，然后在你想要添加过滤器的模型中导入它。