Writable nested serializer in django-rest-framework?

Nested Serializer

You can do something like this, define a serializer for Dataitem that can reuse a serializer of the AssetModel model

class AssetModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = AssetModel

    # Fields org and name of AssetModel will be inlcuded by default

class DataitemSerializer(serializers.ModelSerializer):
    class Meta:
        model = Dataitem

    mod = AssetModelSerializer()
        # This is the Dataitem.mod field
        # which is a FK to AssetModel,
        # Now it'll be serilized using the AssetModelSerializer
        # and include the org and name fields of AssetModelSerializer

I prefer this approach because of the control I get. If you serialize using the above you get a structure like this:

data_item = {'name': ..., 'mod': {'org': ..., 'name': ...}}
                          ^
                          |___ AssetModel fields

Alternatively you can also use depth = n

You can also use depth = 1 in Dataitem

class DataitemSerializer(serializers.ModelSerializer):
        class Meta:
            model = Dataitem
            depth = 1 # Will include fields from related models
                      # e.g. the mod FK to AssetModel

Writable Nested Serializer

Because the behavior of nested creates and updates can be ambiguous, and may require complex dependencies between related models, REST framework 3 requires you to always write these methods explicitly.

We have to implement create/update to make this writable as per DRF's documentation

class DataitemSerializer(serializers.ModelSerializer):
    class Meta:
        model = Dataitem

    # Nested serializer
    mod = AssetModelSerializer()

    # Custom create()
    def create(self, validated_data):
        # First we create 'mod' data for the AssetModel
        mod_data = validated_data.pop('mod')
        asset_model = AssetModel.objects.create(**mod_data)

        # Now we create the Dataitem and set the Dataitem.mod FK
        dataitem = Dataitem.objects.create(mod=asset_model, **validated_data)

        # Return a Dataitem instance
        return dataitem

There seems to be a library that does this drf-writable-nested

it handles the creation and serialisation of these types

  • OneToOne (direct/reverse)
  • ForeignKey (direct/reverse)
  • ManyToMany (direct/reverse excluding m2m relations with through model)
  • GenericRelation (this is always only reverse)

Tags:

Python

Rest

Django

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