在 Django Rest（嵌套序列化程序）中 POST 后 ForeignKey 为空

Question

我是 Django 的新手，我已经实现了一对多的关系，但是嵌套的一个字段为空。

当我发布 destinations 在响应部分中为空。以下是我的回复部分：

{
    "id": 7,
    "name": "Germany tour",
    "description": "This is a fascinating tour to take",
    "price": "30.0",
    "destinations": null,
    "capacity": 10
}

这是我在邮递员的正文部分发帖的方式：

{
    "name": "Germany tour",
    "description": "This is a fascinating tour to take",
    "price": 30.0,
    "destinations": [
        {
            "location":"Germany",
            "tour_type":"Adventure",
            "danger_type":"Medium"
        }
],
    "capacity": 10
}

然后，下面是我的 models 文件：

from django.db import models


class Destinations(models.Model):
    location = models.CharField(max_length=20)
    tour_type = models.CharField(max_length=20)
    danger_type = models.CharField(max_length=20)

    class Meta:
        unique_together = ['location', 'tour_type']


class TourPackages(models.Model):
    name = models.CharField(max_length=50)
    description = models.TextField()
    price = models.DecimalField(max_digits=9, decimal_places=1)
    destinations = models.ForeignKey(Destinations, related_name="destinations", on_delete=models.CASCADE)
    capacity = models.IntegerField()
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.name

然后，我的 serializers 文件：

from rest_framework import serializers
from .models import TourPackages, Destinations


class DestinationSerializer(serializers.ModelSerializer):
    class Meta:
        model = Destinations
        fields = ['tour_type', 'danger_type']


class TourPackagesSerializer(serializers.ModelSerializer):
    destinations = DestinationSerializer(many=True)

    class Meta:
        model = TourPackages
        fields = ['id', 'name', 'description', 'price', 'destinations', 'capacity']

    def create(self, validated_data):
        destination_data = validated_data.pop("destinations")
        location = TourPackages.objects.create(**validated_data)

        for dest_data in destination_data:
            Destinations.objects.create(location=location, **dest_data)

        return location

最后是我的 views 文件：

from rest_framework import generics

from .models import TourPackages
from .serializer import TourPackagesSerializer


class TourList(generics.ListCreateAPIView):
    queryset = TourPackages.objects.all()
    serializer_class = TourPackagesSerializer


class TourDetail(generics.RetrieveUpdateDestroyAPIView):
    queryset = TourPackages.objects.all()
    serializer_class = TourPackagesSerializer

我想要的是发布所有数据并返回响应

Answer 1

您需要先创建Destinations 对象，以便在ForeignKey 的情况下分配它们。从您发布的示例数据来看，这意味着您可以拥有多个 destinations 并且您在其上设置了 on_delete=models.CASCADE。假设对于一个特定的旅行，您有4 目的地并且您决定删除其中两个，那么models.CASCADE 将尝试删除您的tours 对象。如果发生这种情况，剩余的2 目的地对象将指向哪里？ Database integrity 将丢失。所以Django 不允许这样做。您可以通过将ForeignKey 更改为ManyToManyField 来修复。 而你的TourPackagesSerializer 应该是这样的：

基于 Ananya 的回答：

class TourPackagesSerializer(serializers.ModelSerializer):
    destinations = DestinationSerializer(many=True)

    class Meta:
        model = TourPackages
        fields = ['id', 'name', 'description', 'price', 'destinations', 'capacity']

    def create(self, validated_data):
        destination_data = validated_data.pop('destinations')
        dest_obj_list = []
        for dest_data in destination_data:
            dest_obj = Destinations.objects.create(**dest_data)
            dest_obj_list.append(dest_obj)
        location = TourPackages.objects.create(**validated_data)
        location.destinations.set(dest_obj_list)
        location.save()
        return location

Answer 2

在 create 方法中，您正在创建目标对象，但未在位置设置外键。试试这个：

def create(self, validated_data):
    destination_data = validated_data.pop('destinations')
    dest_obj_list = []
    for dest_data in destination_data:
        dest_obj = Destinations.objects.create(location=location, **dest_data)
        dest_obj_list.append(dest_obj)
    location = TourPackages.objects.create(**validated_data)
    location.destinations.set(dest_obj_list)
    location.save()