Django admin 中用于计算字段的自定义过滤器

Question

# models.py

class Author(models.Model):
   name = models.CharField(max_length=50)

class Book(models.Model):
   title = models.CharField(max_length=50)
   created_time = models.DateTimeField(auto_now=False, auto_now_add=True)
   writer = models.ForeignKey(Author, on_delete=models.CASCADE, related_name='books')

# admin.py

@admin.register(Author)
class AuthorAdmin(admin.ModelAdmin):

    def get_queryset(self, request):
        qs = super(AuthorAdmin, self).get_queryset(request)
        return qs.annotate(books_count=Count('books'))

    def books_count(self, inst):
        return inst.books_count

    list_display = ['author', 'books_count']

Now I have two columns in admin: Author and Books count .

I need to add DateFieldListFilter , but for a calculated field (not for model field).

For example, to have a possibility show created books count by each author for last_week , last_month , last_year , etc.

Answer 1

Old question, and you've likely found the answer already, but I literally just did this today (mostly) - I don't think you'd be able to get a count with a filter, as that's not really what a filter does in Django admin; but the quantity of results that have been returned with the filter/s applied does show on the page already

From what I've found, Calculated Fields can be used with list_display in your ModelAdmin - exactly as you've done with books_count

But to create a custom Filter , you have to use a subclass and work with queries instead; which makes sense if you think about the inner workings of what's going on

Hopefully someone finds this useful!

from django.contrib import admin
from datetime import datetime, timedelta

class DateFieldListFilter(admin.SimpleListFilter):
    title = 'Book Count Filter'
    parameter_name = 'books_count'

    def lookups(self, request, model_admin):
        return (
            ('last_week', 'Last Week'),
            ('last_month', 'Last Month'),
            ('last_year', 'Last Year'),
        )

    def queryset(self, request, queryset):
        value = self.value()
        today = datetime.today().date()

        if value == 'last_week':
            start_date = today - timedelta(days=7)
            return queryset.filter(created__gte=start_date)
        elif value == 'last_month':
            start_of_month = today.replace(day=1)
            end_of_last_month = start_of_month - timedelta(days=1)
            start_date = end_of_last_month.replace(day=today.day)
            return queryset.filter(created__gte=start_date)
        elif value == 'last_year':
            start_date = today.replace(year=today.year - 1)
            return queryset.filter(created__gte=start_date)

        return queryset

@admin.register(Author)
class AuthorAdmin(admin.ModelAdmin):
    list_display = ['author', 'books_count']
    list_filter = (DateFieldListFilter,)

    def get_queryset(self, request):
        qs = super(AuthorAdmin, self).get_queryset(request)
        return qs.annotate(books_count=Count('books'))

    def books_count(self, inst):
        return inst.books_count