如何跳过 DRF 序列化程序 FloatField 的验证

Question

问题

我需要添加将minimum_commission 保存为正数的功能，但 None 也可用。我已经添加了序列化器：

class Appartement(models.Model):
    minimum_commission = models.FloatField(null=True, default=None)

class RentalTestSerializer(serializers.ModelSerializer):
    minimum_commission = serializers.FloatField(required=False, min_value=0)

    class Meta:
        model = Appartement
        fields = (
            'minimum_commission',
        )

但是当我从表单（或外壳）传递空字符串时，我看到A valid number is required 验证错误。

In [21]: ser = RentalTestSerializer(data={'minimum_commission': ''})

In [22]: ser.is_valid()
Out[22]: False

In [23]: ser.errors
Out[23]:
ReturnDict([('minimum_commission',
             [ErrorDetail(string=u'A valid number is required.', code=u'invalid')])])

可能的解决方案

起初我添加了自定义字段：BlankableFloatField，它将空字符串转换为无：

class BlankableFloatField(serializers.FloatField):
    """
    We wanted to be able to receive an empty string ('') or 'null' for a float field
    and in that case turn it into a None number
    """
    def to_internal_value(self, data):
        if data in ['', 'null']:
            return None

        return super(BlankableFloatField, self).to_internal_value(data)

并添加了自定义验证：

class RentalTestSerializer(serializers.ModelSerializer):
    minimum_commission = BlankableFloatField(required=False)

    class Meta:
        model = Appartement
        fields = (
            'minimum_commission',
        )

    def validate_minimum_commission(self, value):
        if value and value < 0:
            raise serializers.ValidationError(_("Minimum commission should be greater than 0"))
        return value

现在它按预期工作：

In [38]: ser = RentalTestSerializer(data={'minimum_commission': ''})

In [39]: ser.is_valid()
Out[39]: True

但我认为有没有办法让它更优雅？

---

更新：

正如我所见，主要问题是从表单中传递空字符串。我需要它来重置minimum_commission 列。所以，最终的解决方案是：

class Appartement(models.Model):
    # I have added the blank=True and validator
    minimum_commission = models.FloatField(null=True, default=None, blank=True, validators=[MinValueValidator(0.0)]) 

class RentalTestSerializer(serializers.ModelSerializer):
    # I continue to use the custom field to transform empty space to the None 
    # but instead of custom validation just added the allow_null=True and min_value validator.
    minimum_commission = BlankableFloatField(required=False, allow_null=True, min_value=0)

    class Meta:
        model = Appartement
        fields = (
            'minimum_commission',
        )

---

UPD2：

在了解了处理空字符串的解决方案后，我发现更清楚的是完全跳过在前端发送空字符串并将default=None设置为序列化器。此外，不再需要自定义字段。

class Appartement(models.Model):
    minimum_commission = models.FloatField(null=True, default=None) 

class RentalTestSerializer(serializers.ModelSerializer):
    minimum_commission = serializer.FloatField(required=False, allow_null=True, min_value=0, default=None)

    class Meta:
        model = Appartement
        fields = (
            'minimum_commission',
        )

Answer 1

就像我在评论中提到的 - 公寓模型会很有用。

但是如果我理解正确的话，你想要实现的应该很简单，如下所示：

class Appartement(models.Model):
    minimum_commission = models.FloatField(blank=True, null=True, default=None)

class RentalTestSerializer(serializers.ModelSerializer):

    class Meta:
        model = Appartement
        fields = (
            'minimum_commission',
        )

有了这个实现，minimum_commission 是可选的，它也接受空值。