Django多表关联序列化API报错：'Store'无'Storeimage'属性

问题场景 #

调用关联Store、Storeimage、Address三个模型的REST API时抛出异常，异常信息：

'Store' object has no attribute 'Storeimage'

现有模型代码 #

class Store(models.Model):
    user = models.ForeignKey(User, default=1, null=True, on_delete=models.SET_NULL)
    address = models.ForeignKey(Address, null=True,on_delete=models.CASCADE)
    store_name = models.CharField(max_length=255)
    store_about = models.CharField(max_length=255,null=True)
    store_location = models.CharField( max_length=255)
    store_phoneno = models.CharField(max_length=12)

class Storeimage(models.Model):
    store = models.ForeignKey(Store, null=True, on_delete=models.SET_NULL)
    picture = models.ImageField(upload_to='store_image/%Y/%m/',max_length=255,null=True)

class Address(models.Model):
    street = models.TextField()
    country = models.ForeignKey(Country, default=1,null=True,  on_delete=models.CASCADE)
    state = models.ForeignKey(State, default=1,null=True, on_delete=models.CASCADE)

现有序列化代码 #

class StoreGetSerialiser(serializers.ModelSerializer):
    address = AddressSerializer()
    Storeimage = StoreImage(many=True)
    owner = UserPublicSerializer(source='user', read_only=True)
    class Meta:
        model = Store
        fields = [
            'pk',
            'owner',
            'store_name',
            'Storeimage',
            'store_location',
            'address',
            'store_phoneno',
            'store_website',
        ]

class StoreImage(serializers.ModelSerializer):
    class Meta:
        model = Storeimage
        fields = '__all__'

错误原因 #

Django中外键的反向关联默认名称是模型名小写+_set。这里Storeimage模型关联Store，所以Store对象的反向关联属性是storeimage_set，而非序列化代码中写的Storeimage（大小写错误且不符合默认命名规则）。同时预期输出需要的字段名是store_image，需对应调整。

另外，原序列化代码中的store_website字段在Store模型中不存在，需移除，否则会引发额外错误。

修正方案 #

提供两种可行的修正方式：

方式1：不修改模型，通过source指定反向关联属性 #

修改序列化代码，将字段名改为store_image，并通过source指向正确的反向关联属性：

class StoreGetSerialiser(serializers.ModelSerializer):
    address = AddressSerializer()
    # 用source指定默认反向关联属性storeimage_set，字段名改为预期的store_image
    store_image = StoreImage(many=True, source='storeimage_set')
    owner = UserPublicSerializer(source='user', read_only=True)
    
    class Meta:
        model = Store
        fields = [
            'pk',
            'owner',
            'store_name',
            'store_image',
            'store_location',
            'address',
            'store_phoneno',
            # 移除模型中不存在的store_website字段
        ]

class StoreImage(serializers.ModelSerializer):
    class Meta:
        model = Storeimage
        fields = ['pk', 'picture']  # 只返回预期输出需要的字段

方式2：修改模型，添加related_name自定义反向关联名称 #

在Storeimage模型的外键中添加related_name='store_image'，这样可以直接使用store_image作为序列化字段名：

# 修改Storeimage模型
class Storeimage(models.Model):
    store = models.ForeignKey(Store, null=True, on_delete=models.SET_NULL, related_name='store_image')
    picture = models.ImageField(upload_to='store_image/%Y/%m/',max_length=255,null=True)

对应的序列化代码：

class StoreGetSerialiser(serializers.ModelSerializer):
    address = AddressSerializer()
    store_image = StoreImage(many=True)
    owner = UserPublicSerializer(source='user', read_only=True)
    
    class Meta:
        model = Store
        fields = [
            'pk',
            'owner',
            'store_name',
            'store_image',
            'store_location',
            'address',
            'store_phoneno',
            # 移除模型中不存在的store_website字段
        ]

class StoreImage(serializers.ModelSerializer):
    class Meta:
        model = Storeimage
        fields = ['pk', 'picture']

修正后预期输出 #

{
    "pk": 2,
    "owner": {
        "id": 1
    },
    "store_name": "",
    "store_location": "",
    "address": {
        "id": 14,
        "street": "1",
        "country": 1,
        "state": 1,
        "city": 1
    },
    "store_phoneno": "",
    "store_image": [{"pk":1,"picture":"/location/abcd"},{"pk":2,"picture":"/location/abcd"}]
}

内容的提问来源于stack exchange，提问作者selvakumar