DRF 创建新对象并链接到（但不创建）它的相关项（嵌套序列化程序）？

Question

我正在尝试将多个项目（子域）链接到正在创建的项目（证据）。

我的表单提交正常 - 但我正在尝试找出解决此问题的“最佳”方法。

According to the docs 我必须重写 create 方法 - 但他们的示例显示他们“创建”相关对象。

我不想那样做。我只想将这些相关项目添加到我正在创建的证据中（以创建关系）

这是我的序列化程序：

class SubdomainSerializer(serializers.ModelSerializer):
    class Meta:
        model = Subdomain
        fields = [
            "id",
            "domain",
            "short_description",
            "long_description",
            "character_code",
        ]


class EvidenceSerializer(serializers.ModelSerializer):
    """
    """

    created_by = serializers.HiddenField(
        default=serializers.CurrentUserDefault()
    )
    updated_by = serializers.HiddenField(
        default=serializers.CurrentUserDefault()
    )
    absolute_url = serializers.SerializerMethodField()
    created_by_name = serializers.SerializerMethodField()
    updated_by_name = serializers.SerializerMethodField()
    subdomains = SubdomainSerializer(many=True)

    class Meta:
        model = Evidence
        fields = "__all__"
        extra_kwargs = {
            "subdomains": {
                "error_messages": {
                    "null": "This field is required.",
                    "blank": "This field is required.",
                }
            },
        }

    def get_absolute_url(self, obj):
        return obj.get_absolute_url()

    def get_created_by_name(self, obj):
        return obj.created_by.full_name

    def get_updated_by_name(self, obj):
        return obj.updated_by.full_name

    def create(self, validated_data):
        subdomains_data = validated_data.pop("subdomains")
        evidence = Evidence.objects.create(**validated_data)
        for subdomain in subdomains_data:
            # This is where I want to add the subdomains to the evidence - not create ones - how best to accomplish that?
            Subdomain.objects.create(**subdomain)
        return evidence

    def update(self, instance, validated_data):
        # Add the requestor as the updater in a PATCH request
        request = self.context["request"]
        validated_data["updated_by"] = request.user
        return super().update(instance, validated_data)

有没有更好的方法来设置我的序列化程序？我应该做一些不同的事情来使这更容易实现吗？

编辑添加我的模型：

class Subdomain(CreateUpdateMixin):
    """

    """

    domain = models.ForeignKey(Domain, on_delete=models.PROTECT)
    short_description = models.CharField(max_length=100)
    long_description = models.CharField(max_length=250)
    character_code = models.CharField(max_length=5)
    proficiency_levels = models.ManyToManyField(SubdomainProficiencyLevel)

    class Meta:
        verbose_name = "Subdomain"
        verbose_name_plural = "Subdomains"

    def __str__(self):
        """Unicode representation of Subdomain."""
        return f"{self.character_code}"

class Evidence(CreateUpdateMixin, CreateUpdateUserMixin, SoftDeletionModel):
    """

    """

    subdomains = models.ManyToManyField(Subdomain, related_name="evidences")
    evaluation = models.ForeignKey(
        Evaluation, related_name="evidences", on_delete=models.PROTECT
    )
    published = models.BooleanField(default=False)
    comments = models.CharField(max_length=500)

    class Meta:
        ordering = ["-created_at"]
        verbose_name = "Evidence"
        verbose_name_plural = "Evidence"

    def __str__(self):
        """Unicode representation of Evidence."""
        return f"{self.subdomain} : {self.comments}"

    def get_absolute_url(self):
        """Return absolute url for Evidence."""
        return reverse("evidence-detail", args=[str(self.id)])

Answer 1

在这里您想将subdomain ForeignKey 设置为新创建的evidence。 为此，您只需检索子域并像这样更新他的证据字段：

def create(self, validated_data):
    subdomains_data = validated_data.pop("subdomains")
    evidence = Evidence.objects.create(**validated_data)
    for subdomain in subdomains_data:
        # Retrieve the subdomain and update the evidence attribute
        sub_id = subdomain['id']
        sub = Subdomain.objects.get(id=sub_id)
        sub.evidence = evidence
        sub.save()
    return evidence

注意：我使用默认的反向 ForeignKey 关系：sub.evidence