Question

I have Slide and Chart models, and slides can contain only 1 chart. When serializing the data it fails with the below error:

AttributeError: Got AttributeError when attempting to get a value for field csv on serializer ChartSerializer. The serializer field might be named incorrectly and not match any attribute or key on the RelatedManager instance. Original exception text was: 'RelatedManager' object has no attribute 'csv'.

However, if I simply change:

chart = ChartSerializer(many=True)

in my SlideSerializer (code below) it works. This makes the 'chart' property a list in JSON though when it should be an object as there can only be one Chart, not many (or in this case one) chart objects in a list.

Here are my models (extracts of relevant info only):

# models.py

...

class Slide(models.Model):
    TYPE_MEDIA = 'media'
    TYPE_CHART = 'chart'
    TYPE_CHOICES = (
        (TYPE_MEDIA, 'Media'),
        (TYPE_CHART, 'Chart'),
    )

    title = models.CharField(max_length=255,)

    type = models.CharField(choices=TYPE_CHOICES, max_length=5, default=TYPE_MEDIA)

    media = models.FileField(
        verbose_name='media',
        upload_to='slides',
        null=True,
        blank=True,
    )

    internal_only = models.BooleanField(default=False)

    creation_date = models.DateTimeField(auto_now_add=True)
    modified_date = models.DateTimeField(auto_now=True)


class Chart(models.Model):
    slide = models.ForeignKey(Slide, related_name='chart')

    csv = models.FileField(
        verbose_name='csv',
        upload_to='charts'
    )

    vertical_label = models.CharField(max_length=255,)
    horizontal_label = models.CharField(max_length=255,)

    creation_date = models.DateTimeField(auto_now_add=True)
    modified_date = models.DateTimeField(auto_now=True)


class ChartSeriesLabel(models.Model):
    """Series label associated with a chart"""

    chart = models.ForeignKey(Chart, related_name='serieslabels')

    number = models.CharField(max_length=255,)
    label = models.CharField(max_length=255,)

    creation_date = models.DateTimeField(auto_now_add=True)
    modified_date = models.DateTimeField(auto_now=True)


class ChartDataLabel(models.Model):
    """Data label associated with a chart"""

    chart = models.ForeignKey(Chart, related_name='datalabels')

    date = models.DateField()
    label = models.CharField(max_length=255,)

    creation_date = models.DateTimeField(auto_now_add=True)
    modified_date = models.DateTimeField(auto_now=True)

And my serializers:

# serializers.py

...

class SeriesLabelSerializer(serializers.ModelSerializer):
    class Meta:
        model = ChartSeriesLabel
        fields = ('number', 'label',)


class DataLabelSerializer(serializers.ModelSerializer):
    class Meta:
        model = ChartDataLabel
        fields = ('date', 'label',)


class ChartSerializer(serializers.ModelSerializer):
    serieslabels = SeriesLabelSerializer(many=True)
    datalabels = DataLabelSerializer(many=True)

    class Meta:
        model = Chart
        fields = ('csv', 'vertical_label', 'horizontal_label', 'serieslabels', 'datalabels')


class SlideSerializer(serializers.ModelSerializer):
    chart = ChartSerializer()

    class Meta:
        model = Slide
        fields = ('title', 'type', 'media', 'chart')

Output with chart = ChartSerializer(many=True) in SlideSerializer:

...

{
    "title": "Slide 3",
    "type": "chart",
    "media": null,
    "chart": [
        {
            "csv": "/media/commodities/Hall_of_Fame_Inductees.csv",
            "vertical_label": "Vert",
            "horizontal_label": "Horiz",
            "serieslabels": [
                {
                    "number": "1",
                    "label": "One"
                },
                {
                    "number": "2",
                    "label": "Two"
                },
                {
                    "number": "3",
                    "label": "Three"
                }
            ],
            "datalabels": [
                {
                    "date": "2015-07-22",
                    "label": "This"
                },
                {
                    "date": "2015-07-23",
                    "label": "That"
                },
                {
                    "date": "2015-07-31",
                    "label": "The other"
                }
            ]
        }
    ]
},

...

Note that chart is a JSON list indicating that it could be many charts

Expected output with chart = ChartSerializer() in SlideSerializer:

...

{
    "title": "Slide 3",
    "type": "chart",
    "media": null,
    "chart": {
        "csv": "/media/commodities/Hall_of_Fame_Inductees.csv",
        "vertical_label": "Vert",
        "horizontal_label": "Horiz",
        "serieslabels": [
            {
                "number": "1",
                "label": "One"
            },
            {
                "number": "2",
                "label": "Two"
            },
            {
                "number": "3",
                "label": "Three"
            }
        ],
        "datalabels": [
            {
                "date": "2015-07-22",
                "label": "This"
            },
            {
                "date": "2015-07-23",
                "label": "That"
            },
            {
                "date": "2015-07-31",
                "label": "The other"
            }
        ]
    }
},

...

But instead it throws the error above.

Answer 1

你写的一切都很好。处理嵌套表示应该是项列表，您应该将many=True标志传递给嵌套的序列化程序。访问 http://www.django-rest-framework.org/api-guide/serializers/#dealing-with-nested-objects

所以你需要通过：

chart = ChartSerializer(many=True)

Django Rest Framework: AttributeError when Serializer many=False, but not when many=True

1 个答案: