Python 如何在Django REST Framework ModelSerializer的创建函数中使用field.set（）？

我有一个名为

RoomMarket

的中间模型，连接两个相关模型<代码>市场-

房间市场

-

房间

。当我试图使用可写嵌套序列化程序插入

RoomMarket

的记录时，我遇到了一个错误：

/room_markets/
禁止直接分配到多对多集合的前端。改为使用regions.set（）

这是我简化的

模型.py

：

class RecordStatus:
    published = 'Published'
    drafted = 'Drafted'
    hidden = 'Hidden'
    status = [
        (published, 'Published'),
        (drafted, 'Drafted'),
        (hidden, 'Hidden'),
    ]


class Market(models.Model, RecordStatus):
    name = models.CharField(max_length=100)
    regions = models.ManyToManyField(Region)
    languages = models.ManyToManyField(Language)
    status = models.CharField(max_length=20, choices=RecordStatus.status, default=RecordStatus.published)

    @property
    def get_product_variations(self):
        return Product.objects.filter(distributor__region__market=self).distinct().count()


class Room(models.Model, RecordStatus):
    style = models.ForeignKey(Style, on_delete=models.CASCADE)
    markets = models.ManyToManyField(Market, through='RoomMarket')
    image = models.ImageField(upload_to='room_images', width_field=None, height_field=None,
                              max_length=250, null=True, blank=True)
    name = models.CharField(max_length=50)
    status = models.CharField(max_length=20, choices=RecordStatus.status, default=RecordStatus.published)


class RoomMarket(models.Model):
    market = models.ForeignKey(Market, on_delete=models.CASCADE)
    room = models.ForeignKey(Room, on_delete=models.CASCADE)
    landing_page = models.BooleanField(blank=True, null=True)

    def __str__(self):
        return '%s - %s' % (self.market, self.room)

class CustomRelatedField(serializers.RelatedField):
    def display_value(self, instance):
        return instance

    def to_representation(self, value):
        return str(value)

    def to_internal_value(self, data):
        model = self.queryset.model
        return model.objects.get(id=data)


class MarketSerializer(serializers.ModelSerializer):
    regions = CustomRelatedField(many=True, queryset=Region.objects.all())
    languages = CustomRelatedField(many=True, queryset=Language.objects.all())
    variation = serializers.ReadOnlyField(source='get_product_variations')
    landing_page = serializers.SerializerMethodField(source='get_landing_page')

    class Meta:
        model = Market
        fields = ['id', 'regions', 'languages', 'name', 'status', 'variation', 'landing_page']
        depth = 1

    @staticmethod
    def get_landing_page(market):
        queryset = RoomMarket.objects.filter(market=market)
        if queryset.exists():
            for r in queryset:
                return r.room.id
        else:
            return '-'


class RoomSerializer(serializers.ModelSerializer):
    style = CustomRelatedField(many=False, queryset=Style.objects.all())
    markets = CustomRelatedField(many=True, queryset=Market.objects.all())

    class Meta:
        model = Room
        fields = ['id', 'markets', 'style', 'image', 'name', 'status']


class RoomMarketSerializer(serializers.ModelSerializer):
    market = MarketSerializer()
    room = CustomRelatedField(many=False, queryset=Room.objects.all())

    class Meta:
        model = RoomMarket
        fields = ['id', 'market', 'room', 'landing_page']

    def create(self, validated_data):
        # create market data for Market model.
        market_data = validated_data.pop('market')
        market = Market.objects.create(**market_data)

        # create RoomMarket and set market FK.
        room_market = RoomMarket.objects.create(market=market, **validated_data)

        # return RoomMarket instance.
        return room_market

class RoomMarketView(viewsets.ModelViewSet):
    permission_classes = [permissions.DjangoModelPermissions]
    queryset = RoomMarket.objects.all()
    serializer_class = RoomMarketSerializer

这是我的

序列化程序.py

：

class RecordStatus:
    published = 'Published'
    drafted = 'Drafted'
    hidden = 'Hidden'
    status = [
        (published, 'Published'),
        (drafted, 'Drafted'),
        (hidden, 'Hidden'),
    ]


class Market(models.Model, RecordStatus):
    name = models.CharField(max_length=100)
    regions = models.ManyToManyField(Region)
    languages = models.ManyToManyField(Language)
    status = models.CharField(max_length=20, choices=RecordStatus.status, default=RecordStatus.published)

    @property
    def get_product_variations(self):
        return Product.objects.filter(distributor__region__market=self).distinct().count()


class Room(models.Model, RecordStatus):
    style = models.ForeignKey(Style, on_delete=models.CASCADE)
    markets = models.ManyToManyField(Market, through='RoomMarket')
    image = models.ImageField(upload_to='room_images', width_field=None, height_field=None,
                              max_length=250, null=True, blank=True)
    name = models.CharField(max_length=50)
    status = models.CharField(max_length=20, choices=RecordStatus.status, default=RecordStatus.published)


class RoomMarket(models.Model):
    market = models.ForeignKey(Market, on_delete=models.CASCADE)
    room = models.ForeignKey(Room, on_delete=models.CASCADE)
    landing_page = models.BooleanField(blank=True, null=True)

    def __str__(self):
        return '%s - %s' % (self.market, self.room)

class CustomRelatedField(serializers.RelatedField):
    def display_value(self, instance):
        return instance

    def to_representation(self, value):
        return str(value)

    def to_internal_value(self, data):
        model = self.queryset.model
        return model.objects.get(id=data)


class MarketSerializer(serializers.ModelSerializer):
    regions = CustomRelatedField(many=True, queryset=Region.objects.all())
    languages = CustomRelatedField(many=True, queryset=Language.objects.all())
    variation = serializers.ReadOnlyField(source='get_product_variations')
    landing_page = serializers.SerializerMethodField(source='get_landing_page')

    class Meta:
        model = Market
        fields = ['id', 'regions', 'languages', 'name', 'status', 'variation', 'landing_page']
        depth = 1

    @staticmethod
    def get_landing_page(market):
        queryset = RoomMarket.objects.filter(market=market)
        if queryset.exists():
            for r in queryset:
                return r.room.id
        else:
            return '-'


class RoomSerializer(serializers.ModelSerializer):
    style = CustomRelatedField(many=False, queryset=Style.objects.all())
    markets = CustomRelatedField(many=True, queryset=Market.objects.all())

    class Meta:
        model = Room
        fields = ['id', 'markets', 'style', 'image', 'name', 'status']


class RoomMarketSerializer(serializers.ModelSerializer):
    market = MarketSerializer()
    room = CustomRelatedField(many=False, queryset=Room.objects.all())

    class Meta:
        model = RoomMarket
        fields = ['id', 'market', 'room', 'landing_page']

    def create(self, validated_data):
        # create market data for Market model.
        market_data = validated_data.pop('market')
        market = Market.objects.create(**market_data)

        # create RoomMarket and set market FK.
        room_market = RoomMarket.objects.create(market=market, **validated_data)

        # return RoomMarket instance.
        return room_market

class RoomMarketView(viewsets.ModelViewSet):
    permission_classes = [permissions.DjangoModelPermissions]
    queryset = RoomMarket.objects.all()
    serializer_class = RoomMarketSerializer

这是我的

视图。py

：

class RecordStatus:
    published = 'Published'
    drafted = 'Drafted'
    hidden = 'Hidden'
    status = [
        (published, 'Published'),
        (drafted, 'Drafted'),
        (hidden, 'Hidden'),
    ]


class Market(models.Model, RecordStatus):
    name = models.CharField(max_length=100)
    regions = models.ManyToManyField(Region)
    languages = models.ManyToManyField(Language)
    status = models.CharField(max_length=20, choices=RecordStatus.status, default=RecordStatus.published)

    @property
    def get_product_variations(self):
        return Product.objects.filter(distributor__region__market=self).distinct().count()


class Room(models.Model, RecordStatus):
    style = models.ForeignKey(Style, on_delete=models.CASCADE)
    markets = models.ManyToManyField(Market, through='RoomMarket')
    image = models.ImageField(upload_to='room_images', width_field=None, height_field=None,
                              max_length=250, null=True, blank=True)
    name = models.CharField(max_length=50)
    status = models.CharField(max_length=20, choices=RecordStatus.status, default=RecordStatus.published)


class RoomMarket(models.Model):
    market = models.ForeignKey(Market, on_delete=models.CASCADE)
    room = models.ForeignKey(Room, on_delete=models.CASCADE)
    landing_page = models.BooleanField(blank=True, null=True)

    def __str__(self):
        return '%s - %s' % (self.market, self.room)

class CustomRelatedField(serializers.RelatedField):
    def display_value(self, instance):
        return instance

    def to_representation(self, value):
        return str(value)

    def to_internal_value(self, data):
        model = self.queryset.model
        return model.objects.get(id=data)


class MarketSerializer(serializers.ModelSerializer):
    regions = CustomRelatedField(many=True, queryset=Region.objects.all())
    languages = CustomRelatedField(many=True, queryset=Language.objects.all())
    variation = serializers.ReadOnlyField(source='get_product_variations')
    landing_page = serializers.SerializerMethodField(source='get_landing_page')

    class Meta:
        model = Market
        fields = ['id', 'regions', 'languages', 'name', 'status', 'variation', 'landing_page']
        depth = 1

    @staticmethod
    def get_landing_page(market):
        queryset = RoomMarket.objects.filter(market=market)
        if queryset.exists():
            for r in queryset:
                return r.room.id
        else:
            return '-'


class RoomSerializer(serializers.ModelSerializer):
    style = CustomRelatedField(many=False, queryset=Style.objects.all())
    markets = CustomRelatedField(many=True, queryset=Market.objects.all())

    class Meta:
        model = Room
        fields = ['id', 'markets', 'style', 'image', 'name', 'status']


class RoomMarketSerializer(serializers.ModelSerializer):
    market = MarketSerializer()
    room = CustomRelatedField(many=False, queryset=Room.objects.all())

    class Meta:
        model = RoomMarket
        fields = ['id', 'market', 'room', 'landing_page']

    def create(self, validated_data):
        # create market data for Market model.
        market_data = validated_data.pop('market')
        market = Market.objects.create(**market_data)

        # create RoomMarket and set market FK.
        room_market = RoomMarket.objects.create(market=market, **validated_data)

        # return RoomMarket instance.
        return room_market

class RoomMarketView(viewsets.ModelViewSet):
    permission_classes = [permissions.DjangoModelPermissions]
    queryset = RoomMarket.objects.all()
    serializer_class = RoomMarketSerializer

我用于发布数据的JSON格式：

{
    "market": {
        "regions": [1,2],
        "languages": [1,2],
        "name": "Asia",
        "status": "Published"
    },
    "room": 2,
    "landing_page": true
}

---

我已经读过一些关于这个问题的SO问题，但大多数情况下都是在

ModelSerializer

类中的Form/View而不是

create

函数上。我应该在中间模型

ModelSerializer

类的

create

函数中更改什么？

问题是，当您创建

market

实例时，您将

region

和

language

对象传递给

create（）

方法。您应该将其传递给

set（）

：

def create(self, validated_data):
    # create market data for Market model.
    market_data = validated_data.pop('market')
    regions = market_data.pop("regions")
    languages = market_data.pop("languages")
    market = Market.objects.create(**market_data)
    market.regions.set(regions)
    market.languages.set(languages)

---

谢谢@neverwanner向我解释。我可以将此应用于

更新

功能吗？因为我确信我还需要明确定义

update

函数。@Nathan欢迎！当然你可以在更新中使用它。但是请注意，

set（）

替换相关对象集。如果您不需要它，可能最好在

update（）

中使用

add（）

。有关更多详细信息，请查看文档的相关部分：