Django rest框架未使用FK创建对象到具有unique = True字段的模型 [英] Django rest framework not creating object with FK to a model with unique=True field

问题描述

我有两个这样的模型：

class Sector(models.Model):
    name = models.CharField(max_length=100, db_index=True, unique=True)  # HERE IF I REMOVE unique=True, it works correctly

class Address(models.Model):
    ...
    sector = models.ForeignKey(Sector, null=True, blank=True)

地址模型的序列化器：

在视图中，我有以下内容：

In the view, I have this:

    address_serialized = AddressSerializer(data=request.data)
    if address_serialized.is_valid():
        address_serialized.save(client=client)

它永远不会进入 create 函数。我有一个使用create函数进行序列化的代码，如下所示：

It never gets to the create function. I have a serialized with a create function that looks like this:

class AddressSerializer(serializers.ModelSerializer):
    city_gps = CitySerializer(required=False)
    sector = SectorSerializer(required=False)

    class Meta:
        model = Address
        fields = (..., "sector")

    def create(self, validated_data):
        ...
        sector_dict = validated_data.get("sector", None)   
        sector = None

        if sector_dict and "name" in sector_dict and city_gps:
            if Sector.objects.filter(name=sector_dict["name"], city=city_gps).exists():
                sector = Sector.objects.get(name=sector_dict["name"], city=city_gps)

        # pdb.set_trace()
        if "sector" in validated_data:
            validated_data.pop("sector")
        if "city_gps" in validated_data:
            validated_data.pop("city_gps")

        address = Address.objects.create(sector=sector, city_gps=city_gps, **validated_data)

        return address

代码从不触及此函数， is_valid（）返回False。消息是

The code never touches this function, is_valid() returns False. And the message is

{ sector：{ name：[具有该名称的扇区已经存在。]}}

{"sector":{"name":["sector with this name already exists."]}}

我需要能够使用FK为现有部门创建一个新地址。我该如何实现？任何建议都会有所帮助。

I need to be able to create a new address with FK to the already existing sector. How can I achieve that? Any advice will help.

编辑

视图如下所示：

class ClientProfileAddressCreateView(APIView):
    # throttle_scope = '1persecond'
    renderer_classes = (JSONRenderer,)
    permission_classes = (IsAuthenticated,)

    def post(self, request):

        try:
            client = Client.objects.get(user=request.user)
        except ObjectDoesNotExist:
            return Response({"error": "A client profile for the logged user does not exit"},
                            status=status.HTTP_404_NOT_FOUND)

        address_serialized = AddressSerializer(data=request.data)
        print("address_serialized.is_valid: %s" % address_serialized.is_valid())  # Returns False when unique=True in models
        if address_serialized.is_valid():
            # print("address_serialized: %s" % address_serialized.data)
            address_serialized.save(client=client)
        else:
            return Response(data=address_serialized.errors, status=status.HTTP_400_BAD_REQUEST)

        return Response(data=address_serialized.data, status=status.HTTP_201_CREATED)

推荐答案

这是一个已知问题具有嵌套的序列化程序和独特的约束。

This is a known issue with nested serializers and unique constraints.

真正要做的事情实际上是打印序列化程序-这样可以给您很多额外的信息。

Really awesome thing to always do is actually print the Serializer - that can give you a lot of extra info.

当您拥有这样的json：

When you have a json like this:

{
    "Sector": {
        "name": "Sector XYZ"
    },
    "address_line_one": "Some Random Address"
}

Django REST框架不知道您是要创建还是获取Sector对象，因此它会强制对每个请求进行验证。

Django REST framework does not know whether you're creating or getting the Sector object, thus it forces validation on every request.

您需要执行的操作如下：

What you need to do is the following:

class SectorSerializer(serializers.ModelSerializer):
    # Your fields.
    class Meta:
        model = Address
        fields = ("Your Fields",)

        extra_kwargs = {
            'name': {
                'validators': [],
            }
        }

然后处理验证，您将需要重做创建/更新部分以适应唯一性约束并引发异常/验证错误。

Then to handle validation you would need to redo the create/update part to fit the uniqueness constraint and raise exception/validation error.

我希望这会有所帮助。

I hope this helps.

有用的链接：此SO答案和在嵌套序列化程序中使用唯一约束进行处理

编辑：

根据cezar的要求：我将添加重写序列化器的 create 方法的外观。我没有尝试过这段代码，但是逻辑是这样的。

As per cezar's request: I will add how it might look like to override the create method of the serializer. I have not tried this code, but the logic goes like this.

class SectorSerializer(serializers.ModelSerializer):
    # Your fields.
    class Meta:
        model = Address
        fields = ("Your Fields",)

        extra_kwargs = {
            'name': {
                'validators': [],
            }
        }

    def create(self, validated_data):
        raise_errors_on_nested_writes('create', self, validated_data)

        ModelClass = self.Meta.model

        info = model_meta.get_field_info(ModelClass)
        many_to_many = {}
        for field_name, relation_info in info.relations.items():
            if relation_info.to_many and (field_name in validated_data):
                many_to_many[field_name] = validated_data.pop(field_name)

        # FIELD CHECK
        your_field = validated_data.get("your_field","") # or validated_data["your_field"] 
        try:
            YourModel.objects.filter(your_check=your_field).get()
            raise ValidationError("Your error")
        except YourModel.DoesNotExist:
            # if it doesn't exist it means that no model containing that field exists so pass it. You can use YourQuerySet.exists() but then the logic changes
            pass

        try:
            instance = ModelClass.objects.create(**validated_data)
        except TypeError:
            tb = traceback.format_exc()
            msg = (
                'Got a `TypeError` when calling `%s.objects.create()`. '
                'This may be because you have a writable field on the '
                'serializer class that is not a valid argument to '
                '`%s.objects.create()`. You may need to make the field '
                'read-only, or override the %s.create() method to handle '
                'this correctly.\nOriginal exception was:\n %s' %
                (
                    ModelClass.__name__,
                    ModelClass.__name__,
                    self.__class__.__name__,
                    tb
                )
            )
            raise TypeError(msg)

        # Save many-to-many relationships after the instance is created.
        if many_to_many:
            for field_name, value in many_to_many.items():
                field = getattr(instance, field_name)
                field.set(value)

        return instance

这篇关于Django rest框架未使用FK创建对象到具有unique = True字段的模型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！