Django Rest Framework：动态返回字段子集

时间：2014-05-13 23:22:59

标签： django django-rest-framework

问题

根据blogpost Best Practices for Designing a Pragmatic RESTful API的建议，我想在基于Django Rest Framework的API中添加fields查询参数，使用户只能选择每个资源的字段子集。

实施例

串行：

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

常规查询将返回所有字段。

GET /identities/ 

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

具有fields参数的查询应仅返回字段的子集：

GET /identities/?fields=id,data 

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

包含无效字段的查询应忽略无效字段或抛出客户端错误。

目标

这是否可以开箱即用？如果没有，那么实现这个的最简单方法是什么？是否有第三方包已经这样做了？

10 个答案:

答案 0 :(得分：87)

您可以覆盖序列化程序__init__方法，并根据查询参数动态设置fields属性。您可以在整个上下文中访问request对象，并传递给序列化程序。

在这里，我创建了一个可重用的mixin，它可以进行动态fields修改。

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')

答案 1 :(得分：41)

此功能可从3rd-party package获得。

pip install djangorestframework-queryfields

声明你的序列化器：

from rest_framework.serializers import ModelSerializer
from drf_queryfields import QueryFieldsMixin

class MyModelSerializer(QueryFieldsMixin, ModelSerializer):
    ...

然后，现在可以使用查询参数指定字段（客户端）：

GET /identities/?fields=id,data

排除过滤也是可能的，例如，返回除 id：

之外的每个字段 
GET /identities/?fields!=id

免责声明：我是作者/维护者。

答案 2 :(得分：6)

的 serializers.py 

class DynamicFieldsSerializerMixin(object):

    def __init__(self, *args, **kwargs):
        # Don't pass the 'fields' arg up to the superclass
        fields = kwargs.pop('fields', None)

        # Instantiate the superclass normally
        super(DynamicFieldsSerializerMixin, self).__init__(*args, **kwargs)

        if fields is not None:
            # 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(DynamicFieldsSerializerMixin, serializers.HyperlinkedModelSerializer):

    password = serializers.CharField(
        style={'input_type': 'password'}, write_only=True
    )

    class Meta:
        model = User
        fields = ('id', 'username', 'password', 'email', 'first_name', 'last_name')


    def create(self, validated_data):
        user = User.objects.create(
            username=validated_data['username'],
            email=validated_data['email'],
            first_name=validated_data['first_name'],
            last_name=validated_data['last_name']
        )

        user.set_password(validated_data['password'])
        user.save()

        return user

的 views.py 

class DynamicFieldsViewMixin(object):

 def get_serializer(self, *args, **kwargs):

    serializer_class = self.get_serializer_class()

    fields = None
    if self.request.method == 'GET':
        query_fields = self.request.QUERY_PARAMS.get("fields", None)

        if query_fields:
            fields = tuple(query_fields.split(','))


    kwargs['context'] = self.get_serializer_context()
    kwargs['fields'] = fields

    return serializer_class(*args, **kwargs)



class UserList(DynamicFieldsViewMixin, ListCreateAPIView):
    queryset = User.objects.all()
    serializer_class = UserSerializer

答案 3 :(得分：3)

配置新的分页序列化程序类

from rest_framework import pagination, serializers

class DynamicFieldsPaginationSerializer(pagination.BasePaginationSerializer):
    """
    A dynamic fields implementation of a pagination serializer.
    """
    count = serializers.Field(source='paginator.count')
    next = pagination.NextPageField(source='*')
    previous = pagination.PreviousPageField(source='*')

    def __init__(self, *args, **kwargs):
        """
        Override init to add in the object serializer field on-the-fly.
        """
        fields = kwargs.pop('fields', None)
        super(pagination.BasePaginationSerializer, self).__init__(*args, **kwargs)
        results_field = self.results_field
        object_serializer = self.opts.object_serializer_class

        if 'context' in kwargs:
            context_kwarg = {'context': kwargs['context']}
        else:
            context_kwarg = {}

        if fields:
            context_kwarg.update({'fields': fields})

        self.fields[results_field] = object_serializer(source='object_list',
                                                       many=True,
                                                       **context_kwarg)


# Set the pagination serializer setting
REST_FRAMEWORK = {
    # [...]
    'DEFAULT_PAGINATION_SERIALIZER_CLASS': 'DynamicFieldsPaginationSerializer',
}

制作动态序列化程序

from rest_framework import serializers

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

    See:
        http://tomchristie.github.io/rest-framework-2-docs/api-guide/serializers
    """

    def __init__(self, *args, **kwargs):
        # Don't pass the 'fields' arg up to the superclass
        fields = kwargs.pop('fields', None)

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

        if fields:
            # 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)
# Use it
class MyPonySerializer(DynamicFieldsModelSerializer):
    # [...]

最后，使用homemage mixin为您的APIViews 

class DynamicFields(object):
    """A mixins that allows the query builder to display certain fields"""

    def get_fields_to_display(self):
        fields = self.request.GET.get('fields', None)
        return fields.split(',') if fields else None

    def get_serializer(self, instance=None, data=None, files=None, many=False,
                       partial=False, allow_add_remove=False):
        """
        Return the serializer instance that should be used for validating and
        deserializing input, and for serializing output.
        """
        serializer_class = self.get_serializer_class()
        context = self.get_serializer_context()
        fields = self.get_fields_to_display()
        return serializer_class(instance, data=data, files=files,
                                many=many, partial=partial,
                                allow_add_remove=allow_add_remove,
                                context=context, fields=fields)

    def get_pagination_serializer(self, page):
        """
        Return a serializer instance to use with paginated data.
        """
        class SerializerClass(self.pagination_serializer_class):
            class Meta:
                object_serializer_class = self.get_serializer_class()

        pagination_serializer_class = SerializerClass
        context = self.get_serializer_context()
        fields = self.get_fields_to_display()
        return pagination_serializer_class(instance=page, context=context, fields=fields)

class MyPonyList(DynamicFields, generics.ListAPIView):
    # [...]

请求

现在，当您请求资源时，您可以添加参数fields以仅显示网址中的指定字段。 /?fields=field1,field2

您可以在此处找到提醒：https://gist.github.com/Kmaschta/e28cf21fb3f0b90c597a

答案 4 :(得分：1)

我们在drf_tweaks / control-over-serialized-fields中提供的此类功能。

如果您使用我们的序列化程序，您只需在查询中传递function checkInputs(){ return !$('.input-required').filter(function() { return !this.value; }).length; } 参数。

答案 5 :(得分：0)

您可以尝试Dynamic REST，它支持动态字段（包含，排除），嵌入式/侧载对象，过滤，排序，分页等等。

答案 6 :(得分：0)

对于嵌套数据，我将Django Rest Framework与docs，drf-flexfields

中推荐的软件包一起使用

这允许您限制在父对象和子对象上返回的字段。自述文件中的说明很好，请注意以下几点：

URL似乎需要/这样的'/ person /？expand = country＆fields = id，name，country'，而不是自述文件'/ person？expand = country＆fields = id，name，country'所写

嵌套对象及其相关名称的命名必须完全一致，否则不需要这样做。

例如，如果您有“很多”一个国家可以有很多州，您需要设置“ many”：如文档中所述，在Serializer中为True。

答案 7 :(得分：0)

如果您想要类似于GraphQL的功能，请尝试django-restql，它非常灵活，并且支持嵌套数据（平面和可迭代）。

示例 

from rest_framework import serializers
from django.contrib.auth.models import User
from django_restql.mixins import DynamicFieldsMixin

class UserSerializer(DynamicFieldsMixin, serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ('id', 'username', 'email', 'groups')

常规请求会返回所有字段。

GET /users 

    [
      {
        "id": 1,
        "username": "yezyilomo",
        "email": "yezileliilomo@hotmail.com",
        "groups": [1,2]
      },
      ...
    ]

另一方面，带有query参数的请求仅返回 字段：

GET /users/?query=["id", "username"] 

    [
      {
        "id": 1,
        "username": "yezyilomo"
      },
      ...
    ]

使用 django-restql ，您可以访问任何级别的嵌套字段。例如

GET /users/?query=["id", "username" {"date_joined": ["year"]}] 

    [
      {
        "id": 1,
        "username": "yezyilomo",
        "date_joined": {
            "year": 2018
        }
      },
      ...
    ]

对于可迭代的嵌套字段，例如用户组。

GET /users/?query=["id", "username" {"groups": [[ "id", "name" ]]}] 

    [
      {
        "id": 1,
        "username": "yezyilomo",
        "groups": [
            {
                "id": 2,
                "name": "Auth_User"
            }
        ]
      },
      ...
    ]

答案 8 :(得分：0)

[DRF-Documentation] [1]中建议的解决方案对我有用，但是当我从View调用序列化程序时，方法是： 

class SomeView(ListAPIView):
    def get(self, request, *args, **kwargs):
        qry=table.objects.filter(column_value=self.kwargs['urlparameter'])
        fields=['DBcol1','DBcol2','DBcol3']    
        serializer=SomeSerializer(qry,many=True,fields=fields)

我必须添加many=True，否则它不起作用。

  [1]: https://www.django-rest-framework.org/api-guide/serializers/#example

答案 9 :(得分：0)

另一种选择是使用 GraphWrap：https://github.com/PaulGilmartin/graph_wrap

通过将 /graphql 添加到您的 urlpatterns，您可以使用完全兼容的 GraphQL 可查询 API 添加您的 REST API 层。

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