Django QuerySet returns nothing

问题

I have a list of countries, they all have there own url www.example.com/al/ for example. There is a list of cities for every country but the object_list is empty

My View:

class CityOverview(generic.ListView):
    template_name = 'shisha/pages/country_index.html'
    model = City

    def get_queryset(self, *args, **kwargs):
        country_id = self.kwargs.get('country_id')
        return City.objects.filter(country__name=country_id)

My Model:

class Country(models.Model):
    COUNTRY_CHOICES = (
        ('al', 'Albania'),
        ('ad', 'Andorra'),
        #etc. etc.
    )
    name = models.CharField(max_length=255, choices=COUNTRY_CHOICES, default='nl')

    def __str__(self):
      return self.name

class City(models.Model):
    country = models.ForeignKey(Country, on_delete=models.CASCADE)
    name = models.CharField(max_length=250)

    def __str__(self):
      return self.name

My Urls:

path('<str:country_id>', views.CityOverview.as_view(), name='country'),

My Template:

{{ object_list }}

It returns an empty QuerySet

<QuerySet []>

Does anyone know what the problem is?

回答1:

The problem is you are trying to match country__name to country_id. Alter the last line in get_queryset to become return City.objects.filter(country__id=country_id) which will now filter the country_id supplied against City's country id.

回答2:

May be your returning query is wrong,

class Country(Models.model):
     country_id=Autofield()
     country_name=CharaField()

in Views.py

def get_queryset(self, *args, **kwargs):
    country_id = self.kwargs.get('country_id')
    return City.objects.filter(country_id=country_id)

来源：https://stackoverflow.com/questions/54865487/django-queryset-returns-nothing