Django storage S3 - Save File Path only without file using ModelSerializer - django

Question

I'm using boto3 to upload files to S3 and save their path in the FileField.
class SomeFile(models.Model):
file = models.FileField(upload_to='some_folder', max_length=400, blank=True, null=True)
For the above model the following code works to create a record.
ff = SomeFile(file='file path in S3')
ff.full_clean()
ff.save()
Now, when I use ModelSerializer to do the same.
class SomeFileSerializer(serializers.ModelSerializer):
class Meta:
model = SomeFile
fields = ('file')
I get this error after running the code below
rest_framework.exceptions.ValidationError: {'file': [ErrorDetail(string='The submitted data was not a file. Check the encoding type on the form.', code='invalid')]}
serializer = SomeFileSerializer(data={'file': 'file path to S3'})
serializer.is_valid(raise_exception=True)
I need help in setting up the serializer to accept file path without actually having the file.

Answer 1

I was really in the same situation, and it was hard to find the solution on the web.
We have two options to solve this problem.
1. Passing data directly to save method
Read action: use serializer's read only ImageField
Write action: pass kwargs to save method
serializers.py
from rest_framework import serializers
class SomeFileSerializer(serializers.ModelSerializer):
file = serializers.ImageField(read_only=True)
class Meta:
model = SomeFile
fields = ('file')
views.py
serializer = SomeFileSerializer(data={'file': 'file path to S3'})
serializer.is_valid(raise_exception=True)
# for put method
serializer.save(file=request.data.get('file'))
# for patch method (if partial=True in serializer)
if request.data.get('file'):
serializer.save(file=request.data.get('file'))
else:
serializer.save()
2. Using CharField instead of ImageField
Read action: override to_representation function to response absolute url
Write action: use CharField to avoid ImageField's validation and action
serializers.py
from rest_framework import serializers
class SomeFileSerializer(serializers.ModelSerializer):
file = serializers.CharField(max_length=400)
class Meta:
model = SomeFile
fields = ('file')
def to_representation(self, instance):
representation = super().to_representation(instance)
if instance.file:
# update filename to response absolute url
representation['file'] = instance.file_absolute_url
return representation
models.py
class SomeFile(models.Model):
file = models.FileField(upload_to='some_folder', max_length=400, blank=True, null=True)
#property
def file_absolute_url(self):
return self.file.url if self.file else None
Although I chose the 2nd solution because of drf_spectacular for documentation, the 1st solution would be easy to implement.