python - 在 Django Rest Framework 中的序列化程序之间混合公共(public)字段

Question

我有这个:

class GenericCharacterFieldMixin():
    attributes = serializers.SerializerMethodField('character_attribute')
    skills = serializers.SerializerMethodField('character_skill')

    def character_attribute(self, obj):
        character_attribute_fields = {}
        character_attribute_fields['mental'] = {str(trait_item.get()): trait_item.get().current_value
                                                for trait_item in obj.mental_attributes}
        character_attribute_fields['physical'] = {str(trait_item.get()): trait_item.get().current_value
                                                  for trait_item in obj.physical_attributes}
        character_attribute_fields['social'] = {str(trait_item.get()): trait_item.get().current_value
                                                for trait_item in obj.social_attributes}
        return character_attribute_fields

    def character_skill(self, obj):
        character_skill_fields = {}
        character_skill_fields['mental'] = {str(trait_item.get()): trait_item.get().current_value
                                            for trait_item in obj.mental_skills}
        character_skill_fields['physical'] = {str(trait_item.get()): trait_item.get().current_value
                                              for trait_item in obj.physical_skills}
        character_skill_fields['social'] = {str(trait_item.get()): trait_item.get().current_value
                                            for trait_item in obj.social_skills}
        return character_skill_fields


class MageSerializer(GenericCharacterFieldMixin, serializers.ModelSerializer):
    player = serializers.ReadOnlyField(source='player.username')
    arcana = serializers.SerializerMethodField()

    def get_arcana(self, obj):
        if obj:
            return {str(arcana): arcana.current_value for arcana in obj.linked_arcana.all()}

    class Meta:
        model = Mage
        fields = ('id', 'player', 'name', 'sub_race', 'faction', 'is_published',
                  'power_level', 'energy_trait', 'virtue', 'vice', 'morality', 'size',
                  'arcana', 'attributes', 'skills')
        depth = 1

GenericCharacterFieldMixin 是字符字段的混合，它们是通用的，即对所有类型的字符都是通用的。

我希望我的 Mage Serializer 将这些“混合”而不是 c/p 然后在所有类型的角色之间(Mage 是一种角色)希望这会增加我的 webapp 中的 DRYness。

问题出在我的模型上:

class NWODCharacter(models.Model):

    class Meta:
        abstract = True
        ordering = ['updated_date', 'created_date']

    name = models.CharField(max_length=200)
    player = models.ForeignKey('auth.User', related_name="%(class)s_by_user")
    ....

    def save(self, *args, **kwargs):
        ...

    attributes = GenericRelation('CharacterAttributeLink')
    skills = GenericRelation('CharacterSkillLink')

这意味着我得到了这个错误:

TypeError at /characters/api/mages
<django.contrib.contenttypes.fields.create_generic_related_manager.<locals>.GenericRelatedObjectManager object at 0x00000000051CBD30> is not JSON serializable

Django Rest Framework 认为我想序列化我的通用关系。

如果我重命名模型中的字段(s/attributes/foos/g、s/skills/bars/g)，那么我会得到一个不同的(不太清楚？)错误:

ImproperlyConfigured at /characters/api/mages
Field name `attributes` is not valid for model `ModelBase`.

如何在不混淆 DRF 的情况下将这些方法和字段放入混入中？

Answer 1

设置SerializerMetaclass:

from rest_framework import serializers

class GenericCharacterFieldMixin(metaclass=serializers.SerializerMetaclass):
    # ...

这就是解决方案 recommended by DRF's authors .

前面回答中建议的解决方案是有问题的:

1. user1376455 的解决方案通过在子项上将它们声明为不同的字段来破解 DRF 以在 _declared_fields 中注册 mixin 的字段。此 hack 可能不适用于框架的后续版本。
2. Nikolay Fominyh 的解决方案将 mixin 更改为一个完全成熟的序列化程序(请注意，由于这个原因，名称 GenericCharacterFieldMixin 对于一个不是 mixin 而是序列化程序的类来说是非常不幸的!)。这是有问题的，因为它将完整的 Serializer 类带入多重继承，参见 DRF issue举例说明为什么这是个坏主意。