Django Rest框架：动态返回字段子集 [英] Django Rest Framework: Dynamically return subset of fields

问题描述

如博客设计实用的RESTful API的最佳做法，我想将一个字段查询参数添加到基于Django Rest框架的API这使得用户只能选择每个资源的字段子集。

As recommended in the blogpost Best Practices for Designing a Pragmatic RESTful API, I would like to add a fields query parameter to a Django Rest Framework based API which enables the user to select only a subset of fields per resource.

序列化器：

class IdentitySerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = models.Identity
        fields = ('id', 'url', 'type', 'data')

将返回所有字段。

GET / identity /

[
  {
    "id": 1,
    "url": "http://localhost:8000/api/identities/1/",
    "type": 5,
    "data": "John Doe"
  },
  ...
]

使用字段参数的查询只能返回字段的一个子集：

A query with the fields parameter should only return a subset of the fields:

GET / identities /？fields = id，data

[
  {
    "id": 1,
    "data": "John Doe"
  },
  ...
]

无效字段的查询应忽略无效字段或引发客户端错误。

A query with invalid fields should either ignore the invalid fields or throw a client error.

这是否可以开箱即用？如果没有，最简单的实现方式是什么？有没有第三方软件包已经这样做了？

Is this possible out of the box somehow? If not, what's the simplest way to implement this? Is there a 3rd party package around that does this already?

推荐答案

您可以覆盖串行器 __ init __ 方法，并根据查询参数设置字段属性动态。您可以访问请求对象的上下文，传递给序列化程序。

You can override the serializer __init__ method and set the fields attribute dynamicaly, based on the query params. You can access the request object trouth the context, passed to the serializer.

这里我创建了一个可重用的mixin，修改动态字段

Here I created a reusable mixin, that does the dynamic fields modification.

from rest_framework import serializers

class DynamicFieldsModelSerializer(serializers.ModelSerializer):
    """
    A ModelSerializer that takes an additional `fields` argument that
    controls which fields should be displayed.
    """

    def __init__(self, *args, **kwargs):
        # Instantiate the superclass normally
        super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)

        fields = self.context['request'].QUERY_PARAMS.get('fields')
        if fields:
            fields = fields.split(',')
            # Drop any fields that are not specified in the `fields` argument.
            allowed = set(fields)
            existing = set(self.fields.keys())
            for field_name in existing - allowed:
                self.fields.pop(field_name)


class UserSerializer(DynamicFieldsModelSerializer, serializers.HyperlinkedModelSerializer):

    class Meta:
        model = User
        fields = ('url', 'username', 'email')

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