DRF - Add User to a model with ManyToManyField - django-rest-framework

Question

I am trying to implement a feature to my backend and allow the owner of private "Group" to add other users by their usernames instead of ID's and allow them to add their images to FileField only once after they were added to the model. The code I have so far:
models.py
class Group(models.Model):
group_name = models.CharField(max_length=255)
group_text = models.TextField(max_length=360, blank=True)
owner = models.ForeignKey(
settings.AUTH_USER_MODEL, related_name='owner_user', on_delete=models.SET(get_deleted_user), default=1)
created_on = models.DateTimeField(auto_now_add=True, null=True)
shared_to = models.ManyToManyField(UserProfile, blank=True, related_name='shared_to_user', null=True)
def __str__(self):
return self.group_name
def save(self, *args, **kwargs):
super(Group, self).save(*args, **kwargs)
class GroupImage(models.Model):
group_file = models.FileField(blank=True, null=True,
upload_to='media/covers/%Y/%m/%D/')
gallery_group = models.ForeignKey(Group, related_name='images', on_delete=models.CASCADE)
serializers.py
class GroupImageSerializer(serializers.ModelSerializer):
class Meta:
model = models.GroupImage
fields = ('group_file', )
class SharedToSerializer(serializers.ModelSerializer):
class Meta:
model = models.Group
fields = ('shared_to', )
class GroupSerializer(serializers.ModelSerializer):
images = GroupImageSerializer(many=True, read_only=True)
person = SharedToSerializer(many=True, read_only=True)
class Meta:
model = models.Group
fields = ('id', 'group_name', 'group_text', 'person', 'images')
def create(self, validated_data):
images_data = self.context.get('view').request.FILES
owner_id = self.context['request'].user.id
gallery_group = models.Group.objects.create(group_name=validated_data.get('group_name', 'no-
group_name'), group_text=validated_data.get('group_text'), owner_id=1)
for image_data in images_data.values():
models.GroupImage.objects.create(gallery_group=gallery_group,
group_file=image_data)
return gallery_group
views.py
class GroupCreateAPIView(generics.CreateAPIView):
queryset = models.Group.objects.all()
serializer_class = serializers.GroupSerializer
permission_classes = [AllowAny]

Answer 1

So if your only requirement is how to add users by their username and not their id. You should use SlugRelatedField. I also feel your serializer naming convention is quite confusing. Below is the serializer for Group model that can add users to a group.
class GroupSerializer(Serializer):
... other fields here
shared_to = models.SlugRelatedField(queryset = UserProfile.objects.all(), many=True, slug_field="username", allow_empty=True)
So first checkout SlugRelatedField. This basically is used to map to objects using a specific field of that object(username in this case). You will then get all the UserProfile instances in the shared_to field of the validated_data
property of the serializer which you can fetch in create method and add to you group. And then in the file upload api for your group you can check whether this user belongs to the group or not for permission checking.