Json djangorestframework 3.0 在嵌套序列化程序中创建或更新

首先，您是要支持创建新的图书实例，还是只支持更新现有的图书实例？

If you only ever wanted to create new book instances you could do something like this...

class PageSerializer(serializers.Serializer):
    text = serializers.CharField(max_length=500)

class BookSerializer(serializers.Serializer):
    page = PageSerializer(many=True)
    title = serializers.CharField(max_length=50)

    def create(self, validated_data):
        # Create the book instance
        book = Book.objects.create(title=validated_data['title'])

        # Create or update each page instance
        for item in validated_data['pages']:
            page = Page(id=item['page_id'], text=item['text'], book=book)
            page.save()

        return book

Note that I haven't included the book_id here. When we're creating book instances we won't be including a book id. When we're updating book instances we'll typically include the book id as part of the URL, rather than in the request data.

If you want to support both create and update of book instances then you need to think about how you want to handle pages that are not included in the request, but are currently associated with the book instance.

You might choose to silently ignore those pages and leave them as they are, you might want to raise a validation error, or you might want to delete them.

Let's assume that you want to delete any pages not included in the request.

def create(self, validated_data):
    # As before.
    ...

def update(self, instance, validated_data):
    # Update the book instance
    instance.title = validated_data['title']
    instance.save()

    # Delete any pages not included in the request
    page_ids = [item['page_id'] for item in validated_data['pages']]
    for page in instance.books:
        if page.id not in page_ids:
            page.delete()

    # Create or update page instances that are in the request
    for item in validated_data['pages']:
        page = Page(id=item['page_id'], text=item['text'], book=instance)
        page.save()

    return instance

It's also possible that you might want to only support book updates, and not support creation, in which case, only include the update() method.

也有各种方法可以减少查询的数量.使用批量创建/删除，但上述操作将以相当简单的方式完成工作.

As you can see there are subtleties in the types of behavior you might want when dealing with nested data, so think carefully about exactly what behavior you're expecting in various cases.

还要注意，我在上面的例子中使用了Serializer，而不是ModelSerializer.在这种情况下，只需显式地包含serializer类中的所有字段，而不是依赖ModelSerializer默认生成的自动字段集，就更简单了.