set two fields in the serializer, one with the objects only read, and other
to write. Like this
class ChapterSerializer(ModelSerializer):
uuid = UUIDField(read_only=False)
sections_obj = SectionSerializer(many=True, read_only=True,
source='sections')
class Meta:
model = Chapter
fields = ('uuid', 'description', 'sections', 'sections_obj')
This way you have a serializer nested read/write. You serializer pass the
validation and you manipulate the data in the method create.
Sry my English, I hope you understandme.
On Monday, September 4, 2017 at 12:58:08 PM UTC-3, Markus Hubig wrote:
>
> I'm having a problem creating (nested) serializers for the following
> models:
>
> class Chapter(Model):
> uuid = UUIDField(primary_key=True, editable=False)
> description = TextField(blank=True)
>
> class Section(Model):
> uuid = UUIDField(primary_key=True, editable=False)
> description = TextField(blank=True)
> chapter = ForeignKey(Chapter, related_name='sections', on_delete=CASCADE)
>
>
> Here is the serializer for the Chapter model with the create method:
>
> class ChapterSerializer(ModelSerializer):
> uuid = UUIDField(read_only=False)
> sections = SectionSerializer(many=True, read_only=False)
>
> class Meta:
> model = Chapter
> fields = ('uuid', 'description', 'sections')
>
> def create(self, validated_data):
> sections = validated_data.pop('sections', [])
> chapter = Chapter.objects.create(**validated_data)
>
> for section in sections:
> section.update({'chapter': chapter})
> section = Section.objects.create(**section)
>
> return chapter
>
>
> And here are two slightly different variants of the Section serializer:
>
> class SectionSerializer(ModelSerializer):
> uuid = UUIDField(read_only=False)
> chapter = PrimaryKeyRelatedField(read_only=true)
>
> class Meta:
> model = Section
> fields = ('uuid', 'description', 'chapter')
>
> class SectionSerializer(ModelSerializer):
> uuid = UUIDField(read_only=False)
> chapter = PrimaryKeyRelatedField(queryset=Chapter.objects.all())
>
> class Meta:
> model = Section
> fields = ('uuid', 'description', 'chapter')
>
>
> Now if I try to create a new Chapter with nested Sections and the
> PrimaryKeyRelatedField in the Section serializer has the queryset parameter
> set, I get the following error:
>
> 'sections': [{'chapter': ['Invalid pk "x" - object does not exist.']}]
>
> I think this error is created while converting the pk to an internal value
> <https://github.com/encode/django-rest-framework/blob/master/rest_framework/relations.py#L250>
> but
> actually sounds more like a validation error ...
>
>
> If I use the variant with the read_only=true parameter, creating a new
> Chapter with nested Sections works, but now I can no longer create a new
> Section (Chapter field is set to an existing Chapter UUID) because the
> chapter field is removed while validating the input data.
>
> django.db.utils.IntegrityError: null value in column "chapter_id" violates
> not-null constraint
>
>
> I think I could solve this by duplicating the SectionSerializer, but this
> seems to be a very crude solution ...
>
>
> Overall my experience implementing Nested Serializers with DRF is very
> frustrating! I think one major problem is, that there are very limited
> documentation on this topic! Especially the validation steps are very
> unintuitive, as can be seen in the example above:
>
>
> - Why is the validation step not skipped if I overwrite the validate
> methode?
> - Why is the pk checked while converting to an internal value?
> - Why are read_only fields obmitted (even within the input data to
> self.validate!!!!!) and what can I do about this?
> - How is the internal validation api working? There are many
> methods like run_validation, run_validators, to_internal_value,
> validate, validate_empty_values, validators. How are they working
> together?
> (Any why are they always getting in my way?)
>
>
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