Python M2M字段Django Rest框架嵌套序列化程序上的更新方法

我的models.py中有三个模型，如下所示：

class Service(models.Model):
     name = models.CharField(max_length=50, unique=True)
     port = models.PositiveSmallIntegerField()
     protocol = models.CharField(max_length=50)

class ServiceGroup(models.Model):
     name = models.CharField(max_length=50, unique=True)
     services = models.ManyToManyField(Service, through=ServiceToServiceGroup)

class ServiceToServiceGroup(models.Model):
    service = models.ForeignKey(Service)
    service_group = models.ForeignKey(ServiceGroup)

    {
    "name": "test_service_group1",
    "services":["service_1", "service_2"],
    }

class ServiceGroupCreateUpdateSerializer(serializers.ModelSerializer):
    services = serializers.SlugRelatedField(queryset=Service.objects.all(), 
                                            slug_field='name', many=True)
    class Meta:
        model = ServiceGroup
        fields = ['id', 'name', 'services']

    def create(self, validated_data):
        # Pop the services list out
        services = validated_data.pop('services', None)
        # Create the ServiceGroup with the name 
        service_group = ServiceGroup.objects.create(name=validated_data['name'])
        #Create M2M associations
        for service in services:
            service_id = Service.objects.get(name=service)
            ServiceToServiceGroup.objects.create(service_id=service_id,
                                                 service_group_id= service_group.id)

创建新服务组的JSON有效负载如下所示：

class Service(models.Model):
     name = models.CharField(max_length=50, unique=True)
     port = models.PositiveSmallIntegerField()
     protocol = models.CharField(max_length=50)

class ServiceGroup(models.Model):
     name = models.CharField(max_length=50, unique=True)
     services = models.ManyToManyField(Service, through=ServiceToServiceGroup)

class ServiceToServiceGroup(models.Model):
    service = models.ForeignKey(Service)
    service_group = models.ForeignKey(ServiceGroup)

    {
    "name": "test_service_group1",
    "services":["service_1", "service_2"],
    }

class ServiceGroupCreateUpdateSerializer(serializers.ModelSerializer):
    services = serializers.SlugRelatedField(queryset=Service.objects.all(), 
                                            slug_field='name', many=True)
    class Meta:
        model = ServiceGroup
        fields = ['id', 'name', 'services']

    def create(self, validated_data):
        # Pop the services list out
        services = validated_data.pop('services', None)
        # Create the ServiceGroup with the name 
        service_group = ServiceGroup.objects.create(name=validated_data['name'])
        #Create M2M associations
        for service in services:
            service_id = Service.objects.get(name=service)
            ServiceToServiceGroup.objects.create(service_id=service_id,
                                                 service_group_id= service_group.id)

因为我有一个M2M直通表，所以我创建新服务组的策略是首先弹出服务列表，用名称创建服务组，然后创建M2M Realationships

创建新服务组的序列化程序如下所示：

class Service(models.Model):
     name = models.CharField(max_length=50, unique=True)
     port = models.PositiveSmallIntegerField()
     protocol = models.CharField(max_length=50)

class ServiceGroup(models.Model):
     name = models.CharField(max_length=50, unique=True)
     services = models.ManyToManyField(Service, through=ServiceToServiceGroup)

class ServiceToServiceGroup(models.Model):
    service = models.ForeignKey(Service)
    service_group = models.ForeignKey(ServiceGroup)

    {
    "name": "test_service_group1",
    "services":["service_1", "service_2"],
    }

class ServiceGroupCreateUpdateSerializer(serializers.ModelSerializer):
    services = serializers.SlugRelatedField(queryset=Service.objects.all(), 
                                            slug_field='name', many=True)
    class Meta:
        model = ServiceGroup
        fields = ['id', 'name', 'services']

    def create(self, validated_data):
        # Pop the services list out
        services = validated_data.pop('services', None)
        # Create the ServiceGroup with the name 
        service_group = ServiceGroup.objects.create(name=validated_data['name'])
        #Create M2M associations
        for service in services:
            service_id = Service.objects.get(name=service)
            ServiceToServiceGroup.objects.create(service_id=service_id,
                                                 service_group_id= service_group.id)

我的问题是现在如何编写更新方法？我的JSON负载保持不变，唯一的区别是在URL中传递实例id。伪代码如下：

class Service(models.Model):
     name = models.CharField(max_length=50, unique=True)
     port = models.PositiveSmallIntegerField()
     protocol = models.CharField(max_length=50)

class ServiceGroup(models.Model):
     name = models.CharField(max_length=50, unique=True)
     services = models.ManyToManyField(Service, through=ServiceToServiceGroup)

class ServiceToServiceGroup(models.Model):
    service = models.ForeignKey(Service)
    service_group = models.ForeignKey(ServiceGroup)

    {
    "name": "test_service_group1",
    "services":["service_1", "service_2"],
    }

class ServiceGroupCreateUpdateSerializer(serializers.ModelSerializer):
    services = serializers.SlugRelatedField(queryset=Service.objects.all(), 
                                            slug_field='name', many=True)
    class Meta:
        model = ServiceGroup
        fields = ['id', 'name', 'services']

    def create(self, validated_data):
        # Pop the services list out
        services = validated_data.pop('services', None)
        # Create the ServiceGroup with the name 
        service_group = ServiceGroup.objects.create(name=validated_data['name'])
        #Create M2M associations
        for service in services:
            service_id = Service.objects.get(name=service)
            ServiceToServiceGroup.objects.create(service_id=service_id,
                                                 service_group_id= service_group.id)

弹出服务列表

将名称保存到实例id

查找链接到服务组的现有服务

对于现有列表和JSON有效负载列表中常见的服务，不执行任何操作

对于现有列表中而非有效负载中的服务，请删除M2M关联

对于不在现有列表和有效负载中的服务，创建M2M关联

对于更新方法来说，这似乎需要做很多工作。有没有更简单的方法

更新

In [145]: instance = ServiceGroup.objects.get(pk=1)                                                                                                                                                                                                                      

In [146]: instance.services.all()                                                                                                                                                                                                                                        
Out[146]: <QuerySet [<Service: test-create442>]>

In [147]: new_services_list = ['test-create398']                                                                                                                                                                                                                         

In [148]: service_objects = 
Service.objects.filter(name__in=new_services_list).all()                                                                                                                                                                                     

In [149]: service_objects                                                                                                                                                                                                                                                
Out[149]: <QuerySet [<Service: test-create398>]>

In [150]: instance.service_set = service_objects                                                                                                                                                                                                                         

In [151]: instance.save()                                                                                                                                                                                                                                                

In [152]: instance.services.all()                                                                                                                                                                                                                                        
Out[152]: <QuerySet [<Service: test-create442>]>

[145]中的

：instance=ServiceGroup.objects.get（pk=1）
在[146]中：instance.services.all（）
出[146]：
在[147]中：新的\u服务\u列表=['test-create398']
在[148]中：服务对象=
Service.objects.filter（name\u in=new\u services\u list）.all（）
In[149]：服务对象
出[149]：
在[150]中：instance.service\u set=service\u对象
在[151]：instance.save（）中
在[152]中：instance.services.all（）
出[152]：

---

因此，我尝试了上述方法，但没有成功

您可以覆盖更新方法

def update(self, instance, validated_data):
    # Pop the services list out
    services = validated_data.pop('services', None)
    instance = super().update(instance, validated_data)
    service_objects = Service.objects.filter(name__in=services).all()
    ServiceToServiceGroup.objects.filter(service_group=instance).delete()
    service_group_obj = []
    for service in service_objects:
        service_group_obj(ServiceToServiceGroup(service=service, service_group=instance))
    ServiceToServiceGroup.objects.bulk_create(service_group_obj)
    return instance

---

这看起来真的很好…你能详细说明一下instance.service_set是如何工作的吗？django使用相关的_名称为关系字段提供反向访问，如果不定义相关的\u名称，默认值为modelname\u set..我尝试了这个..这似乎不起作用..M2M关系没有更新..没有错误..它只是不更新M2M表..还请注意，有一个直通表..更新是否需要通过它进行？更新的字段名称将是服务而不是服务\u set