Django Admin：如何按没有数据库字段的自定义list_display字段之一排序

Question

# admin.py

class CustomerAdmin(admin.ModelAdmin):  

    list_display = ('foo', 'number_of_orders')

# models.py

class Order(models.Model):

    bar = models.CharField[...]

    customer = models.ForeignKey(Customer)

class Customer(models.Model):

    foo = models.CharField[...]

    def number_of_orders(self):

        return u'%s' % Order.objects.filter(customer=self).count()  

如何根据客户对客户进行分类number_of_orders？

admin_order_field属性不能在这里使用，因为它需要一个数据库字段进行排序。Django依赖底层数据库执行排序，这有可能吗？创建一个包含订单数量的汇总字段似乎在这里是过大的。

有趣的是：如果您在浏览器中手动更改url以在此列上进行排序-它将按预期工作！

Answer 1

我喜欢Greg解决此问题的方法，但我想指出，您可以直接在管理员中执行相同的操作：from django.db import modelsclass CustomerAdmin(admin.ModelAdmin):&nbsp; &nbsp; list_display = ('number_of_orders',)&nbsp; &nbsp; def get_queryset(self, request):&nbsp; &nbsp; # def queryset(self, request): # For Django <1.6&nbsp; &nbsp; &nbsp; &nbsp; qs = super(CustomerAdmin, self).get_queryset(request)&nbsp; &nbsp; &nbsp; &nbsp; # qs = super(CustomerAdmin, self).queryset(request) # For Django <1.6&nbsp; &nbsp; &nbsp; &nbsp; qs = qs.annotate(models.Count('order'))&nbsp; &nbsp; &nbsp; &nbsp; return qs&nbsp; &nbsp; def number_of_orders(self, obj):&nbsp; &nbsp; &nbsp; &nbsp; return obj.order__count&nbsp; &nbsp; number_of_orders.admin_order_field = 'order__count'这样，您只需在管理界面内进行注释。并非与您执行的每个查询有关。

Answer 2

我尚未对此进行测试（我想知道它是否有效），但是如何定义一个自定义管理器，Customer其中包括汇总的订单数，然后设置admin_order_field为该汇总，即from django.db import models&nbsp;class CustomerManager(models.Manager):&nbsp; &nbsp; def get_query_set(self):&nbsp; &nbsp; &nbsp; &nbsp; return super(CustomerManager, self).get_query_set().annotate(models.Count('order'))class Customer(models.Model):&nbsp; &nbsp; foo = models.CharField[...]&nbsp; &nbsp; objects = CustomerManager()&nbsp; &nbsp; def number_of_orders(self):&nbsp; &nbsp; &nbsp; &nbsp; return u'%s' % Order.objects.filter(customer=self).count()&nbsp; &nbsp; number_of_orders.admin_order_field = 'order__count'编辑：我刚刚测试了这个想法，它完美地工作-不需要django admin子类化！

Answer 3

我能想到的唯一方法是对字段进行非规范化。也就是说-创建一个实际字段，该字段将进行更新以与它所源自的字段保持同步。我通常通过覆盖带有非规范化字段的模型或其衍生模型来保存：# models.pyclass Order(models.Model):&nbsp; &nbsp; bar = models.CharField[...]&nbsp; &nbsp; customer = models.ForeignKey(Customer)&nbsp; &nbsp; def save(self):&nbsp; &nbsp; &nbsp; &nbsp; super(Order, self).save()&nbsp; &nbsp; &nbsp; &nbsp; self.customer.number_of_orders = Order.objects.filter(customer=self.customer).count()&nbsp; &nbsp; &nbsp; &nbsp; self.customer.save()class Customer(models.Model):&nbsp; &nbsp; foo = models.CharField[...]&nbsp; &nbsp; number_of_orders = models.IntegerField[...]