如果没有提交文件，则获取空Ordereddict

Question

它是我的模型，我想在序列化器中使截图字段可选 -

class SbmWebsiteAdditionalScreenshot(TimeStampedModel):
    website = models.ForeignKey(
        'SbmWebsite', related_name='additional_screenshots')
    screenshot = models.ImageField(
        upload_to='website/interim/additional_screenshot/', blank=True)
    associated_additional_screenshot = models.ForeignKey(
        'websites.WebsiteAdditionalScreenshot',
        related_name='sbn_website_associated_additional_screenshot',
        null=True, editable=False, blank=True)
    request_deletion = models.BooleanField(default=False, editable=False)

我尝试了这三个选项。

1

class SbmWebsiteAdditionalScreenshotSerializer(serializers.ModelSerializer):
    is_interim = serializers.SerializerMethodField()

def get_is_interim(self, obj):
    return True

class Meta:
    model = SbmWebsiteAdditionalScreenshot
    fields = [
            'screenshot', 'associated_additional_screenshot',
            'request_deletion',
            'id', 'is_interim'
            ]

data = [{'id': 28, 'associated_additional_screenshot': None, 'is_interim': True}]

f= SbmWebsiteAdditionalScreenshotSerializer(data=data, many=True)
f.is_valid()
True
f.validated_data[0].items()
[]

2

class SbmWebsiteAdditionalScreenshotSerializer(serializers.ModelSerializer):
is_interim = serializers.SerializerMethodField()
screenshot = serializers.ImageField(required=False)

def get_is_interim(self, obj):
    return True

class Meta:
    model = SbmWebsiteAdditionalScreenshot
    fields = [
            'screenshot', 'associated_additional_screenshot',
            'request_deletion',
            'id', 'is_interim'
            ]

f= SbmWebsiteAdditionalScreenshotSerializer(data=data, many=True)
f.is_valid()
True
f.validated_data[0].items()
[]

3

class SbmWebsiteAdditionalScreenshotSerializer(serializers.ModelSerializer):
is_interim = serializers.SerializerMethodField()
screenshot = ImageField(allow_empty_file=True, use_url=True)

def get_is_interim(self, obj):
    return True

class Meta:
    model = SbmWebsiteAdditionalScreenshot
    fields = [
            'screenshot', 'associated_additional_screenshot',
            'request_deletion',
            'id', 'is_interim'
            ]

f= SbmWebsiteAdditionalScreenshotSerializer(data=data, many=True)
f.is_valid()
False
f.errors
[OrderedDict([('screenshot', [u'No file was submitted.'])])]

如何在不上传图像的情况下使ImageField可选并序列化数据？我要么得到空的dict或错误