DRF nested serializers custom output - serialization

Question

Couldn't find problem like this, so here is my problem:
models.py (simplified)
class Root(models.Model):
name = models.CharField()
class TextFile(models.Model):
root = models.ForeignKey(Root)
name = models.CharField()
class ImageFile(models.Model):
root = models.ForeignKey(Root)
name = models.CharField()
serializers.py
class TextFileSerializer(serializers.Modelserializer):
class Meta:
model = TextFile
fields = '__all__'
class ImageFileSerializer(serializers.Modelserializer):
class Meta:
model = ImageFile
fields = '__all__'
class FilesSerializer(serializers.Modelserializer):
Texts = TextFileSerializer(source='textfile_set', many=True, read_only=True)
Images = ImageFileSerializer(source='imagefile_set', many=True, read_only=True)
class Meta:
model = Root
fields = '__all__'
class RootSerializer(serializers.Modelserializer):
files = FilesSerializer(many=True, read_only=True)
class Meta:
model = Root
fields = '__all__'
I've got only root 'id' and 'name' in output but no 'files'.
I expect output like this:
{
'id': 0,
'name': 'Root instance 1',
'files': {
'Texts': [
{'id': 0, 'name': 'Text1'},
{'id': 1, 'name': 'Text2'},
...
],
'Images': [
{'id': 0, 'name': 'Image1'},
{'id': 1, 'name': 'Image2'},
...
]
}
}
Can anyone help me with that?

Answer 1

Your FilesSerializer field in RootSerializer is always returning None because Root have no property named 'files'. DRF serializer don't add None fields in the response by default. Your FileSerializer ask for a RootModel.
What you want is a way to retrieve files from your root model, so what you can do is using a SerializerMethodField, and in this method, fetch the data you need, and serializer them using your FileSerializer (but as a normal serializer).
Like so :
class TextFileSerializer(serializers.ModelSerializer):
class Meta:
model = TextFile
fields = '__all__'
class ImageFileSerializer(serializers.ModelSerializer):
class Meta:
model = ImageFile
fields = '__all__'
class FilesSerializer(serializers.Serializer):
Texts = TextFileSerializer(source='textfile_set', many=True)
Images = ImageFileSerializer(source='imagefile_set', many=True)
class Meta:
fields = '__all__'
class RootSerializer(serializers.ModelSerializer):
files = serializers.SerializerMethodField()
class Meta:
model = Root
fields = '__all__'
def get_files(self, instance):
return FilesSerializer(instance).data
It returns
[
{
"id": 1,
"files": {
"Texts": [],
"Images": [
{
"id": 1,
"name": "testimage",
"root": 1
}
]
},
"name": ""
}
]