来自 Django Rest Framework 中的中间模型的访问字段

Question

尝试从 DRF 中的中间模型访问字段时遇到困难。

我们来看看相关模型：

class School(models.Model):

    created = models.DateTimeField(auto_now_add=True)
    name = models.CharField(max_length=50, verbose_name=_(u'Name'))

    staff_order = models.ManyToManyField(settings.AUTH_USER_MODEL, verbose_name=_(u'Staff ordering'), through='StaffOrder', related_name='school_staff_order')

class User(AbstractUser):

    phone = models.CharField(max_length=20, blank=True, null=True)
    address = models.CharField(max_length=150, blank=True, null=True)
    about_me = models.CharField(max_length=200, blank=True, null=True)

    REQUIRED_FIELDS = ['email']

    def __unicode__(self):
        return u'{0}'.format(self.username)

class StaffOrder(models.Model):
    user = models.ForeignKey(settings.AUTH_USER_MODEL)
    school = models.ForeignKey(School)
    order = models.PositiveSmallIntegerField(default=0, verbose_name=_(u'Staff ordering for this school'))

    class Meta:
        verbose_name_plural = _(u'Staff ordering')

现在我期望在为用户返回 QuerySet 时能够从 StaffOrder 中读取订单字段（StaffSerializer）。以下是序列化程序：

class StaffRoleSerializer(serializers.ModelSerializer):

    class Meta:
        model = StaffOrder
        fields = (
            'order',
        )


class StaffSerializer(serializers.ModelSerializer):

    username = serializers.CharField(max_length=75, required=True)
    email = serializers.CharField(max_length=75, required=True)
    order = StaffRoleSerializer(source='school_staff_order')

    class Meta:
        model = User

StaffSerializer 按顺序返回的是经理，而不是与此用户相关的 StaffOrder 模型中的订单字段。

Staff 的 JSON 预期响应是这样的：

[
  {
    "username": "Denise",
    "email": "deniseburton@maximind.com",
    "order": 9
  },
  {
    "username": "Ina",
    "email": "inaburton@maximind.com",
    "order": 4
  }
]

我也希望能够从序列化程序中写入这个值，但我可以在 Viewset 中做到这一点，但我真的需要在序列化程序本身中读取这个值......知道我错过了什么在这里？

Answer 1

首先，您必须了解一个用户可以有多个员工订单。在您的模型中，您已经以这种方式定义了它。

要获得您在问题中指定的 json 输出，您需要查询 StaffOrder 对象而不是用户。

class StaffOrderSerializer(serializers.ModelSerializer):
    username = serializers.CharField(source='user.username')
    email = serializers.CharField(source='user.email')

    class Meta:
        model = StaffOrder
        fields = ('order', )

在列表视图中使用此序列化程序类：

class StaffOrderListApi(generics.ListAPIView):
    serializer_class = StaffOrderSerializer

    def get_queryset(self):
        # using distinct because same user can have multiple staff orders
        # based on your example it seems you want distinct users
        return StaffOrder.objects.all().distinct('user')

这将为您提供所需的 json。