BaseSerializer 中的自定义验证器

Question

我想在 BaseSerializer 中使用自定义验证器。

第一次尝试：

自定义验证器:

class UserIdExists:
def __init__(self):
    self.MESSAGE_INCORRECT_USER = 'No user with this id.'

def __call__(self, user_id):
    exists = User.objects.filter(id=user_id).exists()
    if not exists:
            message = self.MESSAGE_INCORRECT_USER
            raise serializers.ValidationError(message, code='invalid')

和BaseSerializer:

class QuestionBaseSerializer(serializers.BaseSerializer):

   def to_internal_value(self, data):
      user_id = data.get('user_id')

      user_validator = UserIdExists()
      user_validator(user_id=user_id)

如果出现验证错误，我收到一条消息：

'["No user with this id."]'

但是我想收到这样一条信息：

'{"user_id": "No user with this id."}'

第二次尝试： 自定义验证器：

class UserIdExists:
    def __init__(self):
        self.MESSAGE_INCORRECT_USER = 'No user with this id.'

    def __call__(self, user_id, field=None):
        exists = User.objects.filter(id=user_id).exists()
        if not exists:
            if field:
                message = {field: self.MESSAGE_INCORRECT_USER}
                raise serializers.ValidationError(message, code='invalid')

        else:
            if not field:
                message = self.MESSAGE_INCORRECT_USER
                raise serializers.ValidationError(message, code='invalid')

和BaseSerializer:

class QuestionBaseSerializer(serializers.BaseSerializer):

    def to_internal_value(self, data):
        user_id = data.get('user_id')

        user_validator = UserIdExists()
        user_validator(user_id=user_id, field='user_id')

我收到预期的消息：

'{"user_id": "No user with this id."}'

我做的对吗？可以做得更正确吗？

Answer 1

与其使用 to_internal_value，不如使用专门用于验证的功能，这样 extend/maintain 会更容易，因为您只需要关注验证逻辑，而不是如何产生内部价值。验证字段的约定是通过：

序列化器字段属性validators（字段的验证器列表运行）
序列化器方法validate_field_name()
序列化器方法validate()

这里为了简化说明，我们将验证只允许奇数user_id。

class UserIdExists:
    def __init__(self):
        self.MESSAGE_INCORRECT_USER = 'No user with this id.'

    def __call__(self, user_id):
        if user_id % 2 == 0:
            raise serializers.ValidationError("No user with this id.")
        return user_id


class QuestionBaseSerializer(serializers.Serializer):
    user_id = serializers.IntegerField(
        validators=[UserIdExists()]
    )


class MathQuestionSerializer(QuestionBaseSerializer):
    description = serializers.CharField()

>>> from my_app.serializers import MathQuestionSerializer
>>>
>>> serializer = MathQuestionSerializer(data={'user_id': 2, 'description': "What is an imaginary number?"})
>>> serializer.is_valid(raise_exception=True)
Traceback (most recent call last):
    raise ValidationError(self.errors)
rest_framework.exceptions.ValidationError: {'user_id': [ErrorDetail(string='No user with this id.', code='invalid')]}
>>> 
>>> serializer = MathQuestionSerializer(data={'user_id': 3, 'description': "What is an imaginary number?"})
>>> serializer.is_valid(raise_exception=True)
True

如您所见，从 QuestionBaseSerializer 继承是有效的，因为它自动正确验证了 user_id 字段，确保它不是偶数。

您可以通过实施 validate_field_name():

选择第二种样式来进一步自定义验证

class QuestionBaseSerializer(serializers.Serializer):
    user_id = serializers.IntegerField()

    def validate_user_id(self, user_id: int) -> int:
        validator = UserIdExists()
        return validator(user_id)


class MathQuestionSerializer(QuestionBaseSerializer):
    description = serializers.CharField()

    def validate_user_id(self, user_id: int) -> int:
        # Let's call the usual validation of even-odd numbers
        user_id_validated = super().validate_user_id(user_id)

        # Now, let's add additional validation of small numbers
        if user_id_validated < 10:
            raise serializers.ValidationError("No user with this id.")
        return user_id_validated

>>> serializer = MathQuestionSerializer(data={'user_id': 2, 'description': "What is an imaginary number?"})
>>> serializer.is_valid(raise_exception=True)
Traceback (most recent call last):
    raise ValidationError(self.errors)
rest_framework.exceptions.ValidationError: {'user_id': [ErrorDetail(string='No user with this id.', code='invalid')]}
>>> 
>>> serializer = MathQuestionSerializer(data={'user_id': 3, 'description': "What is an imaginary number?"})
>>> serializer.is_valid(raise_exception=True)
Traceback (most recent call last):
    raise ValidationError(self.errors)
rest_framework.exceptions.ValidationError: {'user_id': [ErrorDetail(string='No user with this id.', code='invalid')]}
>>> 
>>> serializer = MathQuestionSerializer(data={'user_id': 14, 'description': "What is an imaginary number?"})
>>> serializer.is_valid(raise_exception=True)
Traceback (most recent call last):
    raise ValidationError(self.errors)
rest_framework.exceptions.ValidationError: {'user_id': [ErrorDetail(string='No user with this id.', code='invalid')]}
>>> 
>>> serializer = MathQuestionSerializer(data={'user_id': 15, 'description': "What is an imaginary number?"})
>>> serializer.is_valid(raise_exception=True)
True

如您所见，验证正确地检查了它是否为奇数（基本验证）并且是否大于 10（子类验证）。

BaseSerializer 中的自定义验证器

Custom validators in BaseSerializer

django

serialization

django-rest-framework