从 Django Rest Framework 响应中删除空字段

Question

我使用 django-rest-framework 开发了一个 API。 我正在使用 ModelSerializer 来返回模型的数据。

models.py

class MetaTags(models.Model):
    title = models.CharField(_('Title'), max_length=255, blank=True, null=True)
    name = models.CharField(_('Name'), max_length=255, blank=True, null=True)

serializer.py

class MetaTagsSerializer(serializers.ModelSerializer):
    class Meta:
        model = MetaTags

回复

{
    "meta": {
        "title": null,
        "name": "XYZ"
    }
}

理想情况下，在 API 响应中，任何不存在的值都不应在响应中发送。 当title 是null 时，我希望回复是：

{
    "meta": {
        "name": "XYZ"
    }
}

Answer 1

我发现这个解决方案是最简单的。

from collections import OrderedDict
from rest_framework import serializers

class NonNullModelSerializer(serializers.ModelSerializer):
    def to_representation(self, instance):
        result = super(NonNullModelSerializer, self).to_representation(instance)
        return OrderedDict([(key, result[key]) for key in result if result[key] is not None])

Answer 2

我遇到了类似的问题，解决方法如下：

from operator import itemgetter


class MetaTagsSerializer(serializers.ModelSerializer):
    class Meta:
        model = MetaTags

    def to_representation(self, instance):
        ret = super().to_representation(instance)
        # Here we filter the null values and creates a new dictionary
        # We use OrderedDict like in original method
        ret = OrderedDict(filter(itemgetter(1), ret.items()))
        return ret

或者，如果您只想过滤空字段，您可以将 itemgetter(1) 替换为以下内容：

lambda x: x[1] is not None

Answer 3

CubeRZ 的答案对我不起作用，使用 DRF 3.0.5。我认为 to_native 方法已被删除，现在被 to_representation 取代，在 Serializer 中定义而不是 BaseSerializer。

我在 DRF 3.0.5 中使用了下面的类，它是来自 Serializer 的方法的副本，稍作修改。

from collections import OrderedDict

from rest_framework import serializers
from rest_framework.fields import SkipField

class NonNullSerializer(serializers.ModelSerializer):

    def to_representation(self, instance):
        """
        Object instance -> Dict of primitive datatypes.
        """
        ret = OrderedDict()
        fields = [field for field in self.fields.values() if not field.write_only]

        for field in fields:
            try:
                attribute = field.get_attribute(instance)
            except SkipField:
                continue

            if attribute is not None:
                represenation = field.to_representation(attribute)
                if represenation is None:
                    # Do not seralize empty objects
                    continue
                if isinstance(represenation, list) and not represenation:
                   # Do not serialize empty lists
                   continue
                ret[field.field_name] = represenation

        return ret

EDIT 合并来自 cmets 的代码

Answer 4

您可以尝试覆盖 to_native 函数：

class MetaTagsSerializer(serializers.ModelSerializer):
    class Meta:
        model = MetaTags

    def to_native(self, obj):
        """
        Serialize objects -> primitives.
        """
        ret = self._dict_class()
        ret.fields = self._dict_class()

        for field_name, field in self.fields.items():
            if field.read_only and obj is None:
                continue
            field.initialize(parent=self, field_name=field_name)
            key = self.get_field_key(field_name)
            value = field.field_to_native(obj, field_name)

            # Continue if value is None so that it does not get serialized.
            if value is None:
                continue

            method = getattr(self, 'transform_%s' % field_name, None)
            if callable(method):
                value = method(obj, value)
            if not getattr(field, 'write_only', False):
                ret[key] = value
            ret.fields[key] = self.augment_field(field, field_name, key, value)

        return ret

我基本上从serializers.BaseSerializer 复制了基础 to_native 函数并添加了对值的检查。

更新： 至于 DRF 3.0，to_native() 被重命名为 to_representation() 并且它的实现做了一些改变。这是 DRF 3.0 的代码，它忽略了 null 和空字符串值：

def to_representation(self, instance):
    """
    Object instance -> Dict of primitive datatypes.
    """
    ret = OrderedDict()
    fields = self._readable_fields

    for field in fields:
        try:
            attribute = field.get_attribute(instance)
        except SkipField:
            continue

        # KEY IS HERE:
        if attribute in [None, '']:
            continue

        # We skip `to_representation` for `None` values so that fields do
        # not have to explicitly deal with that case.
        #
        # For related fields with `use_pk_only_optimization` we need to
        # resolve the pk value.
        check_for_none = attribute.pk if isinstance(attribute, PKOnlyObject) else attribute
        if check_for_none is None:
            ret[field.field_name] = None
        else:
            ret[field.field_name] = field.to_representation(attribute)

    return ret

Answer 5

添加了两个选项：

• 删除值为 None 的键
• 删除值为 None 或 Blank 的键。

from collections import OrderedDict
from rest_framework import serializers


# None field will be removed
class NonNullModelSerializer(serializers.ModelSerializer):
    def to_representation(self, instance):
        result = super(NonNullModelSerializer, self).to_representation(instance)
        return OrderedDict([(key, result[key]) for key in result if result[key] is not None])


# None & Blank field will be removed
class ValueBasedModelSerializer(serializers.ModelSerializer):
    def to_representation(self, instance):
        result = super(ValueBasedModelSerializer, self).to_representation(instance)
        return OrderedDict([(key, result[key]) for key in result if result[key] ])

简单地修改基于无和空白值的键删除，对于我 采用。感谢@Simon。