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python - 在 Django 中初始化时拦截和替换序列化器字段

问题描述

所以我有一个带有大量模型的 Django REST 框架的 Django 项目。为了使前端用户友好，我不仅应该显示相关对象的 ID，还应该显示名称。我对解决方案的想法是在响应时用序列化程序中的 StringRelatedFields 替换所有 PrimaryKeyRelated 字段。由于模型的数量很大，我决定制作一个抽象的序列化器/mixin 并拦截字段创建，如果类型正确，则替换该字段。这是我到现在为止的距离：

class AbstractSerializer(serializers.ModelSerializer):
class Meta:
    model: AbstractModel = AbstractModel
    read_only_fields: list = [
        'created_at',
        'created_by',
        'modified_at',
        'modified_by',
        'is_deleted',
        'deleted_at',
        'deleted_by'
    ] + ['is_active'] if 'is_active' in [field.attname for field in model._meta.fields] else []
    abstract: bool = True

def to_representation(self, instance):
    serializer = AbstractRequestResponseSerializer(instance)
    return serializer.data


class AbstractRequestResponseSerializer(AbstractSerializer):

class Meta(AbstractSerializer.Meta):
    pass

@classmethod
def _get_declared_fields(cls, bases, attrs):
    fields = [(field_name, attrs.pop(field_name))
              for field_name, obj in list(attrs.items())
              if isinstance(obj, Field)]
    fields.sort(key=lambda x: x[1]._creation_counter)

    new_fields = []
    for field in fields:
        if isinstance(field, PrimaryKeyRelatedField):
            field = StringRelatedField(source=field.source, required=False)
        new_fields.append(field)
    fields = new_fields

    known = set(attrs)

    def visit(name):
        known.add(name)
        return name

    base_fields = [
        (visit(name), f)
        for base in bases if hasattr(base, '_declared_fields')
        for name, f in base._declared_fields.items() if name not in known
    ]

    return OrderedDict(base_fields + fields)

由于方法的原因，这会产生无限循环错误__new__，我开始怀疑我是否覆盖了正确的函数。我也尝试替换to_representation函数，但我猜当所有字段实例都已创建时，该函数在流程中出现得太晚了。我应该覆盖哪个功能？

标签： pythondjangodjango-rest-frameworkdjango-serializer

解决方案

也许我错误地表述了这个问题（你可以重新表述以帮助后代:)），但我提出的解决方案如下所示：

class AbstractSerializer(serializers.ModelSerializer):
class Meta:
    model: AbstractModel = AbstractModel
    read_only_fields: list = [
        'created_at',
        'created_by',
        'modified_at',
        'modified_by',
        'is_deleted',
        'deleted_at',
        'deleted_by'
    ] + ['is_active'] if 'is_active' in [field.attname for field in model._meta.fields] else []
    abstract: bool = True

def to_representation(self, instance):
    ret = OrderedDict()
    fields = self._readable_fields

    for field in fields:
        if isinstance(field, PrimaryKeyRelatedField):
            parent = field.parent
            field_name = field.field_name
            source = field.source
            if source != field_name:
                field = StringRelatedField(source=field.source, required=False)
            else:
                field = StringRelatedField(required=False)
            field.bind(field_name, parent)
        try:
            attribute = field.get_attribute(instance)
        except SkipField:
            continue

        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

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