django REST 框架 - 嵌套 ModelSerializer 的有限查询集？

Question

我有一个 ModelSerializer，但默认情况下它会序列化我模型中的所有对象。我想将此查询集限制为仅最近的 500 个(而不是全部 5000 万个)。我该怎么做？

我目前有以下内容:

class MyModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = MyModel

我认为我不能只在我的 View 集中指定查询集的原因是，这实际上是另一个序列化程序的嵌套部分。

模型.py

class Container(models.Model):
    size  = models.CharField(max_length=20)
    shape = models.CharField(max_length=20)

class Item(models.Model):
    container = models.ForeignKey(Container, related_name='items')
    name  = models.CharField(max_length=20)
    color = models.CharField(max_length=20)

View .py

class ContainerViewSet(viewsets.ModelViewSet):
    queryset = Container.objects.all()  # only a handful of containers
    serializer_class = ContainerSerializer

序列化器.py

class ItemSerializer(serializers.ModelSerializer):
    class Meta:
        model = Item
        fields = ('name', 'color')

class ContainerSerializer(serializers.ModelSerializer):
    items = ItemSerializer(many=True)  # millions of items per container
    class Meta:
        model = Container
        fields = ('size', 'shape', 'items')

Answer 1

在您的 View 集中，您可以像下面这样指定查询集:

from rest_framework import serializers, viewsets

class MyModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = MyModel

class MyModelViewSet(viewsets.ModelViewSet):
    queryset = MyModel.objects.all()[:500]
    serializer_class = MyModelSerializer

我认为您正在寻找的是 SerializerMethodField .

因此您的代码将如下所示:

class ContainerSerializer(serializers.ModelSerializer):
    items = SerializerMethodField('get_items')

    class Meta:
        model = Container
        fields = ('size', 'shape', 'items')

    def get_items(self, container):
        items = Item.objects.filter(container=container)[:500]  # Whatever your query may be
        serializer = ItemSerializer(instance=items, many=True)
        return serializer.data

一个问题是 SerializerMethodField 是只读的。