Django REST框架：serializer上下文如何工作？ [英] Django REST Framework: how serializer context works?

问题描述

在Django REST框架中，提供额外的 args / kwargs 到序列化程序以设置值是一个非常标准的任务的字段未通过 request.data 设置，但通过url参数或Cookie中的值。例如，我需要在POST请求时将我的注释模型的用户字段设置为等于 request.user 。这些额外的参数被称为上下文。

It's a pretty standard task in Django REST Framework to supply additional args/kwargs to a serializer to set values of fields set not via request.data, but via the value in url parameters or cookies. For instance, I need to set user field of my Comment model equal to request.user upon POST request. Those additional arguments are called context.

几个问题（， 2 ）在StackOverflow上建议我覆盖我的 ModelViewSet get_serializer_context（） C $ C>。我做了，没有帮助。我试图理解，出了什么问题，发现我从源代码中不明白，这个上下文系统应该是如何工作的。 （关于此事的文档也是丢失的）

Several questions (1, 2) on StackOverflow suggest that I override get_serializer_context() method of my ModelViewSet. I did and it doesn't help. I tried to understand, what's wrong, and found out that I don't understand from the source code, how this context system is supposed to work in general. (documentation on this matter is missing, too)

任何人都可以解释，在哪里serializer将上下文添加到正常的请求数据？我找到了两个地方，从中保存了值。

Can anyone explain, where serializer adds context to normal request data? I found two places, where it saves the values from context.

1. serializer.save（），它将kwargs与验证的数据进行混合，但通常调用没有参数（例如通过 ModelMixins ）。


2. 字段。 __ new __（） ，它缓存了args和kwargs，但似乎以后没有人读过。

1. serializer.save(), method, which mixes kwargs with validated data, but it is usually called with no arguments (e.g. by ModelMixins).
2. fields.__new__(), which caches args and kwargs, but it seems that nobody ever reads them later.

推荐答案

每当您使用通用视图或视图集时，DRF（3.3.2）都会添加请求对象，视图对象和格式到序列化程序上下文。您可以使用 serializer.context 访问，让我们在序列化程序中说 request.user 。

Whenever you use generic views or viewsets, DRF(3.3.2) adds request object, view object and format to the serializer context. You can use serializer.context to access, lets say request.user in the serializer.

当 get_serializer_class（）被调用时，这是添加的。在其中，它调用 get_serializer_context（）方法，其中所有这些参数都添加到其上下文中。

This is added when get_serializer_class() is called. Inside that, it calls get_serializer_context() method where all these parameters are added to its context.

DRF源代码供参考：

class GenericAPIView(views.APIView):
    """
    Base class for all other generic views.
    """

    def get_serializer(self, *args, **kwargs):
        """
        Return the serializer instance that should be used for validating and
        deserializing input, and for serializing output.
        """
        serializer_class = self.get_serializer_class()
        kwargs['context'] = self.get_serializer_context()
        return serializer_class(*args, **kwargs)    

    def get_serializer_context(self):
        """
        Extra context provided to the serializer class.
        """
        return {
            'request': self.request,
            'format': self.format_kwarg,
            'view': self
        }

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