Django REST Framework-序列化多对多表关系

Question

我正在为一个网站创建一个API，该网站我有一个带有Books的表，另一个带有Hashtags的表（基本上是hashtags的目录，例如“ #traveling”）和一个中间表，用于在Books之间建立多对多关系和标签。我的模型是：

# models.py
class Books(models.Model):
    id_books = models.AutoField(primary_key=True)
    title = models.CharField(max_length=150)

class Hashtags(models.Model):
    id_hashtags = models.AutoField(primary_key=True)
    hashtag = models.CharField(max_length=150)

class Books_Hashtags(models.Model):
    id_books_hashtags = models.AutoField(primary_key=True)
    id_books = models.ForeignKey(Books, on_delete=models.CASCADE)
    id_hashtags = models.ForeignKey(Hashtags, on_delete=models.CASCADE)
    class Meta:
        unique_together = ("id_books", "id_hashtags")

我想拥有一个提供如下输出的API：

[
    {
        "id_books": 1,
        "title": "The Hobbit",
        "hashtags": [
            {
                "id_hashtags": 1,
                "hashtag": "fantasy"
            },
            {
                "id_hashtags": 2,
                "hashtag": "fiction"
            },
            {
                "id_hashtags": 3,
                "hashtag": "middle earth"
            },
        ]
    }
]    

为此，我在网上找到了一些示例，使用DRF对上述模型进行了序列化：

#serializers.py
from rest_framework import serializers
from app.models import Books, Books_Hashtags, Hashtags

class HashtagsSerializer(serializers.ModelSerializer):
    hashtags = serializers.CharField()
    class Meta:
        model = Hashtags
        fields = ('hashtag',)

class Books_HashtagsSerializer(serializers.ModelSerializer):
    id_hashtag = HashtagsSerializer(many=True, read_only=True)
    class Meta:
        model = Books_Hashtags
        fields = ('id_hashtags',)

class BooksSerializer(serializers.ModelSerializer):
    id_books = serializers.IntegerField()
    id_books_hashtags = Books_HashtagsSerializer(many=True, read_only=True)
    title = serializers.CharField()

    class Meta:
        model = Books
        fields = ('id_books', 'title', 'id_books_hashtags',)

我的看法如下：

#views.py
from ntgBackend.models import Books
from rest_framework import viewsets
from api.serializers import BooksSerializer

class BooksViewSet(viewsets.ModelViewSet):
    serializer_class = BooksSerializer
    queryset = Books.objects.all()

到目前为止，我已经设法从API获得以下输出：

[
    {
        "id_books": 1,
        "title": "The Hobbit",
    }
]

但是没有有关标签的信息，我知道它们存在于数据库中。我正在将DRF 3.8.2与MySQL DB和Django 2.0.2。请帮忙！

Answer 1

我遇到了同样的问题，并通过一些研究得出了以下结论：

在models.py 中，只修改您的Book 模型以包含一个带有Hashtags 的ManyToManyField，使用Books_Hashtagas 作为您的中间表。另外一定要在第一本书之前声明你的Hashtag模型以供参考

# models.py
class Books(models.Model):
    id_books = models.AutoField(primary_key=True)
    title = models.CharField(max_length=150)
    hashtags = models.ManyToManyField(Hashtags, related_name='hashTg', through="Books_Hashtags"

在您的序列化程序文件中，请务必添加 depth = 1 以获得您需要的内容，否则您将只会获得主题标签 ID（这仅适用于 ListAPI）

#serializers.py
class BooksSerializer(serializers.ModelSerializer):
    class Meta:
        model = Books
        #In case you want to filter out some fields:
        #fields = ('field_A','field_B' )
        fields = '__all__'
        depth = 1

在视图中，我使用泛型，因为它们解决了我的大部分需求：

#views.py
from ntgBackend.models import Books
from rest_framework import generics
from api.serializers import BooksSerializer

class BooksViewSet(generics.ListCreateAPIView):
    serializer_class = BooksSerializer
    queryset = Books.objects.all()

我对此很陌生，我希望它有所帮助。除了 Django(2.0.4)，我使用的版本与您几乎相同。

祝你好运