django - 使用与 django-rest-framework 序列化程序的反向关系

Question

我的模型看起来像这样:

class User(TimestampedModel):
    name = models.CharField(max_length=30, null=False, blank=False)
    device = models.CharField(max_length=255, null=False, blank=False)


class Comment(TimestampedModel):
    user = models.ForeignKey(User, on_delete=models.PROTECT, blank=True, null=True)
    contents = models.CharField(max_length=510)
    rating = models.IntegerField(blank=False, null=False)

我的序列化程序如下所示:

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ('name',)


class CommentListItemSerializer(serializers.ModelSerializer):
    user = UserSerializer()

    class Meta:
        model = Comment
        fields = ('user', 'contents', 'rating')

和观点:

class CommentsList(generics.ListAPIView):
    serializer_class = CommentListItemSerializer
    queryset = Comment.objects.all()

它几乎完成了工作;)。我得到的回应是这样的:

"results": [
    {
        "user": {
            "name": "Ania"
        },
        "contents": "Very good",
        "rating": 6
    },
    {
        "user": {
            "name": "Anuk"
        },
        "contents": "Not very good",
        "rating": 1
    }
]

这种 react 有两个问题。

我不想拥有这个嵌套对象“user.name”。我想将其作为一个简单的字符串字段接收，例如 "username" .

序列化程序为每个用户进行数据库查询(不是连接，而是单独的查询)，以获取他/她的姓名。既然这是 Not Acceptable ，如何解决这个问题？

Answer 1

Serializer makes a database query (not a join, but a separate query) for each user, to get his/her name.

您可以 使用 select_related() 在 queryset 你的观点的属性。然后访问 user.name不会导致进一步的数据库查询。

class CommentsList(generics.ListAPIView):
    serializer_class = CommentListItemSerializer
    queryset = Comment.objects.all().select_related('user') # use select_related

I don't want to have this nested object "user.name". I'd like to receive that as a simple string field, for example "username"

您可以 定义只读 username您的序列化程序中的字段 source 争论。这将返回 username场响应。

class CommentListItemSerializer(serializers.ModelSerializer):
    # define read-only username field
    username = serializers.CharField(source='user.name', read_only=True) 

    class Meta:
        model = Comment
        fields = ('username', 'contents', 'rating')